I'm probably more interested in the software used to run 7 VMs like that.
Haven't watched the video as he annoys me too much but I would guess the software is unRAID. I know he has a beta of the next version.
I have been using it for years as a NAS solution but in the latest major version they have made some huge strides forwards with various virtualisation options. I have dabbled with Xen and VMWare for a while with hardware passthrough but Limetech seem to have pretty much nailed it now.
Haven't spent as much time as I would like tweaking it but I am running a Dell T5500 with dual Xeon X5650 CPUs and 60GB of RAM. I have a GTX 960 in there which is passed through to a W7 machine with 8 cores and 16GB of RAM. Haven't tested extensively but works for Steam streaming, just need to get a Steam Link to use on the downstairs TV.