I am also thinking of getting a r410 with 2x 6 core cpu and 64gb ddr3 1333mhz ram ECC for me and my friends to host game servers on. I would also like to know if you could use a normal psu but i myself wouldn't need it. however to run all those VM's I recommend you go with 32gb 8 for Plex on ubuntu VM and 8gb for the rest, 8gb for Minecraft, Windows 10, and your media. should be perfect and the power consumption shouldn't really matter like you said at this point.