I use a configuration like this (with Proxmox) to send content to the various TVs in my house (HDMI over Cat 5e). 4 cheap GPUs in the machine allow for up to 4 VMs running OS X (my preferred OS for media) to simultaneously play HD content, run classic emulated games, web browsing, etc. (haven't bothered with UHD yet, and probably won't for a while).

Of course, a lot of HD content can run with very modest specs (as long as the codecs are accelerated on the GPU), but for occasional content that requires CPU decoding or players/sites that aren't yet supported on standalone devices (Apple TV, Roku, etc), it's a really nice solution. Plus, it keeps each TV very clean in terms of cables and hardware.

I've done hackintosh on bare metal in the past, but even if I were setting up a single-headed hackintosh now, I'd still go the VFIO route - it makes updates much less stressful since you can quickly roll back to a snapshot if you break something.