Yup, linux works on much more hardware than MS-Windows.
nVidia is not a good choice in Linux though, they oppose to the worldwide standards and refuse to cooperate with the developers of open source drivers. SLI makes very little sense in Linux, it's a handicapped and illogical attempt at scaling resources. AMD cards for instance are much stronger in compute applications, and they scale perfectly fine (without any bridge connectors, they just scale to the full extent of the resources on the card, at least on an IOMMU supporting system, which the Intel X-chipset platform is).
With hardware passthrough to a Windows guest, SLI should however work, although - again - there have been several difficulties in implementing nVidia hardware with VGA passthrough, the correct solution there would be PCI passthrough (which should work without much troubles). Generally though, AMD now also supports true colour in Linux, and you get the benefit of HSA and TrueAudio and open standards for variable sync speeds, besides the order of magnitude higher compute performance. There really is no reason to get an nVidia card, especially not such expensive cards. If you're doing this for video rendering, you might want to take a look at some professional software, like the Linux software that is used for actual big budget motion pictures. All things considered, Premiere Pro is pretty slow and consumer-grade-limiting in comparison to some advanced open source solutions (which are free as in free beer, but not not always as in freedom, because there are proprietary codecs involved in video sometimes, that require a proprietary license. That's why this software is available as open source software, so the code can be audited and is safe to use, but you have to register to legally use it, even if you don't even have to register under your real name, and it's also available from the AUR for instance without registering). These are more technical to use, but have much greater performance, make much better use of scaled hardware resources (also clusters for instance, the technique for very fast rendering used by rendering farms, which only use linux and AMD GPU cards of course, and which are hired by video production companies if they need very fast rendering of video materials, for instance for news shows, where every second counts. These rendering farms use surprisingly modest hardware, but stack several machines together in a cluster for a very powerful distributed hybrid computing solution, which is a native functionality in linux. The money otherwise wasted on those Titan Blacks could be used for a scaled system that's much more capable for instance. But I don't know what you want to do exactly of course.
With linux you can't only save on software costs, you can also save on hardware costs, because linux gets more out of any hardware and doesn't wear it down as fast (especially harddrives, and especially SSD's!). You can get more performance out of a system with much cheaper AMD FirePro's and extra PCIe SSD power, and your hardware will last longer, yet you spend more money and you can do more things that the limited Titan Blacks can't do (they have very poor compute support and don't scale nicely, you basically just waste the cost of the memory on the second and third card completely, and that's the biggest extra cost of the cards to begin with).
The best thing you can do for professional video use, is to contact a professional linux integrator that works for some video production entities. They can tell you what hardware would get you the most bang for the buck within your budget, and usually have pretty fair prices for delivering a fully functional linux system with 24/7 same day support, which is taken very seriously in the linux world. Then you'll get a better return on investment than by blowing your budget on Titan Blacks lol. Adobe Premiere Pro is not the most professional video production software, just like Photoshop Lightroom is not the most professional photo production software. It's prosumer software, and in comparison to professional linux solutions, it's pretty oldfashioned, slow, and limited in functionality. That's why movie studios, news studios, professional video production units, etc... don't use Premiere Pro, but use linux based solutions. Of course, they don't have to advertise what they use, because nobody pays them for advertising this or that software, and they have enough income without advertising for this or that software, so you have to do some research on what they use and how they use it.
Same goes for audio production, although that's mainly still a Mac scene in the professional audio world, mainly because you don't need the latest and greatest hardware for audio production, and there has been a technological status quo in audio production for quite some time now, with the exception of the high end broadcasting and cinema scene, that does audio and video production at the same time, which has also switched to linux completely, again with a lot of mixed open source/proprietary solutions because of proprietary codecs (Dolby, DTS, iMAX, etc... are all proprietary systems). In the audio scene, there is also a definite revival of analogue techniques, and that's been going on for quite some time now, and it's not slowing down, quite on the contrary even.
For home production, you don't really need Premiere Pro, but things like Lightworks are more than enough and are easy to use if you're experienced with Premiere Pro. Audio production on Linux is possible on a basic level with Audacity, and on an advanced level with Ardour. There are lots of LADSPA/LV2 plugins of incredible quality available for linux, that work even with simple media players.
In general, a big difference between linux and a closed source commercial software console like MS-Windows, is that linux applications are made to keep all possibilities and compatibilities open for others to build upon. That's why linux applications don't make choices for you or don't automate some things that software console applications do limit or automate. That makes linux applications feel more technical, and sometimes they require a learning curve for people that are used to limiting software console applications. You have to realize that open source has another philosophy than commercial software consoles. Open source software is extremely user-centric, as it's basically made by users for users. It made in order to allow users to produce their product in the most efficient way, whatever their product may be, and allowing users to deploy their specific talent to the largest extent. It's not telling users what to do and how to do it like software console applications do. For some users, this might be overwhelming at first, and it takes time to get used to the degree of freedom and endless possibilities of open source software. Just the Linux operating system itself allows so much more control over every part of the computer, that some people get scared of it, because they are confronted with things they didn't even know where there or where possible.
That's why I would advise to take it slowly when transitioning to Linux. Keep running Windows 7 for a while, get an extra SSD and install Linux on that, separate from your existing software console install. Get used to Linux and open source applications, find your way, explore the freedom and power, take your time... because that's what open source is about: there aren't two open source users that have the same software setup, after a while using open source software, a user always customizes his/her system on a fundamental level, because that's what open source is made to do, it's made to adapt to the user, and not to make the user adapt to a software console. The transition might be more eye-opening and pervasive than you might expect. Most new linux users expect the equivalent of Windows applications. That exists, that's for instance what SteamOS offers, but then that's just another (although linux-based) software console. That is also the case for ChromeOS, which is based on Gentoo Linux, but it's just another software console. Normal linux distros however are not like that, they are meant to be much more than that, they are meant to leverage the talent of the user and allow the user to shape his own ideal computing environment. That's the spirit of open source. Just allow yourself to get used to the idea of endless possibilities, don't just jump into it and scare yourself to death, just to panic and run back to software consoles, which would not be doing yourself a favour lol...