I used win 8.1 for a few days on my MVF and it worked. As for buying the MVF, I guess it depends where you live. You can still buy them in the UK
Intel i7 3770K@ 4.5GHz,
Silverstone Heligon HE01
ASUS Maximus V Formula, 1803 BIOS
16GB Corsair Vengeance 1600 @ 1866MHz, 9-10-9-27
MSI GTX 970
Samsung 250GB SSD
Seagate 500GB 7200 RPM HDD
Antec Earthwatts 650 PSU
NZXT Phantom 630
Win 8 Pro x64