I would recommend ibuypower.com if you don't want to build one yourself, but would still like to control the parts going into it.
and as I said earlier, and will continue to say, there's not really a difference between Windows 7 and Windows 8/8.1 after a google search and a few tweaks it looks and functions the same. It is faster, afterall.
My self build, for reference's sake:
CPU: i7 4770k Intel
RAM: 16 GB Vengeance Corsair DDR3
Primary Storage/OS Drive: 250GB Intel 530 SSD
Secondary Storage: 2TB Seagate Barrucuda
Motherboard: Gigabyte GA-Z87X-UD4H ATX LGA1150
GPU: Radeon R9 280X
Other:....unimportant stuff like blu-ray, fans, card readers, etc etc
OS(es):Windows 8.1/Arch (Linux Distro)
It all depends on budget, if we knew your's it would probably help in finding a computer.