Windows 8 is kind of like windows XP, its a kind of business PC but since most of the companies already have windows XP or upgraded into a mac windows 8 is almost worthless. just stick with win7 i say.
for PC build i would do this
this is from amazon only but if you really want some deals i would say to buy maybe a few from newegg.
For A Good Gaming Pc Here Are A good Specification
CPU: Intel Core i7 920
CPU Cooling: Stock Intel HS&F
Motherboard: ASUS P6T-Deluxe X58
RAM: 6GB (3 x 2GB) G.Skill 1333MHz DDR3
Graphics: Nvidia GeForce GTX 580 1.5GB
Sound: Onboard ADI AD2000B HD Audio Chipset
Monitor: Samsung 24" 2443BW Full LCD
Primary Hard Drive: Western Digital 150GB VelociRaptor SATA2
Secondary Hard Drive: Western Digital 74GB Raptor SATA
Optical Drive: Pioneer DVD-RW 216BK SATA
Updated in Sept. 2010 to: Pioneer BDR-205 Blu-Ray Writer SATA
Keyboard & Mouse: Microsoft Wireless Laser Desktop 7000
Power Supply: Seasonic 700W M12
Case: Cooler Master Stacker 832 SE
OS: Windows 7 Ultimate 64-bit
like i have said, if you can buy from other sites than amazon than you can get a lower price for the build.
some stuff from amazon have pretty good deals but you won't get everything at a good deal from amazon. i suggest trying newegg out as you can get some combo deals and such.(only good thing about amazon is pretty much the free shipping on almost everything and sometimes free tax)