The mac is not certified for 4k with any graphics card. In the config it only has up to 2k support. That’s single channel not stereo. I have a gt120 for gui and GTX480 for processing and am able to do 3D HD quite effectively. Might be able to pull off 2k-3D, but if you seriously want to do 4k-3D with RT performance, Linux seems like your only choice.
That said with HD proxies you could definitely handle grading and reviewing on the mac, and it wouldn’t require the 4000 for gui, though it might not hurt.