To avoid the cost of upgrading my system, and the hassle of doing lookglass… I’m thinking of making a low cost fx 8350 build and putting windows on it… then using an elgato streaming device to view the output of the video card… pairing that with a kvm… would this not be the same thing as lookingglass?
Nevermind, I see from YT videos that this wouldnt work. 
If you’re genuinely curious, you can use a Magewell HDMI Pro Capture 4K LT in low latency mode. USB based solutions though won’t be good. You’re basically trying to do what Streamers call a Dual System Setup, but with a hardware KVM.
Also keep in mind that KVMs hate 1000hz polling rate on gaming mice and keyboards.
I’ve thought about this as well. Its not going to beat looking glass, although what reports I can sort of find on this suggest at least some people think it works well. But some people have a very high tolerance for latency it seems.
Here’s a great review where a guy measured latency of various capture devices:
So you’re going to take a bath on latency to the tune of 40ms or more. It depends upon what elgato device you’re using though, some of them have massive latency counted in seconds and others are among the low latency winners in this chart.
That guy is @eposvox, friend of Level1.
The Magewell with low latency mode is the best bet for Linux.