GTX 580 SLI vs GTX 680 vs 7970

I have a single GTX 580 and I am looking forward to this years new titles, such as Battlefield 4. I am trying to decide whehter I should buy another GTX 580 and do SLI, or get a new GTX 680 or 7970. The problem is I am torn between which will perform better and I also am not sure if a PCI Express 3.0 card will work in my 2.0 motherboard. I have all my specs listed in my profile if you would like to know. So should I go GTX 580 SLI, GTX 680, AMD Radeon 7970, or another card?

Id go 7970 for a gaming rig.

Why's that? And will it fit in my PCI Express 2.0 Port?

Yes PCI Express 3.0 is backwards compatible with PCI Express 2.0 slots.

I would always go One card over SLI/Crossfire for a whole bunch of reasons, and there is little point in getting the 680 over a 7970 if your not going to take advantage of the CUDA cores......(and your priority in the opening post seems to be games over workstation applications that would use CUDA)

Yeah, I don't really need CUDA, my card has 512 CUDA cores and I have never had any programs I used that utilized them. I mainly consume media (movies, music, etc.), play games, and browse the internet. I would prefer getting a card that will last for years and is within a reasonable price. The 7970 is not bad price wise but I have never used any AMD GPUs. What is your opinion on AMD GPUs and do you have any idea what ym PNY Enthusiast Edition GeForce GTX 580 will go for on eBay?

I'm in the same boat as you. I have a GTX 580 and I feel like I should get a second one for SLi. Performance wise it will beat a single 7970 and GTX 680. It is always better to use a single gpu if possible but in this case I feel like going SLi will yield better fps.

AMD cards are fine, there is nothing wrong with using them. If you are looking for a single gpu solution I agree with peps1, 7970.

Oh, I realized I didn't mention this before money is a large factor in all of this. I think I will go with another GTX 580 for SLI because it is cheaper. I can pickup my same exact card for around $250 on eBay so I think I will end up doing that. Thanks for all the suggestions and help. If I ever get a new card it will be AMD, I have no use for all the CUDA cores that come with high end Nvidia cards. I also will only ever be upgrading when I can't run games on at least medium settings with playable FPS (40-above FPS). That will take a few years so I will stick with the SLI for a bit if the eBay deal isn't gone.