i have an old gtx 460 256-bit sitting in my htpc so i'm also open to move that one to this build and getting the new video card for the htpc. if we go that route, i'm looking for suggestions for a good gpu for the htpc (i3 2120 used to watch blurays and hd streaming video). any suggestions? thanks!
I would use the GTX 460 in the video editing computer. It will be excellent and even support CUDA acceleration in certain Adobe software. If you are using something that can support Quicksync, you will want to enable Virtu so that it can pass the video encoding to the HD 4000.
Have you tried the onboard HD 2000 in the i3-2120? It should be more than enough for HD playback.