The high end gaming PC is going to be something that can run everything at 1080P at high to ultra settings. This machine will burn through any game on the market, and will have plenty of room for expansion as well.The best building pc tutorial - http://www.youtube.com/watch?v=ea_bs5G1yYU
CPU – Intel Core i5-3570K
Motherboard – ASUS P8Z77-V Pro
Memory - 8GB Corsair Vengeance 1600MHz DDR3 Low Profile 1.5v Memory
Video Card – Sapphire Radeon HD 7970 Vapor-X
Boot Drive – Crucial m4 128GB SSD
Optical Drive - OEM DVD Drive or OEM Blu Ray Drive (Any Manufacturer)
PSU – XFX ProSeries 850W
Case – Corsair Carbide Series 500R
CPU Cooler – Cooler Master Hyper 212 Evo
Operating System – Windows 7 64 bit
Both of these builds are nice - definitely recommend getting a 250GB or so SSD and passing on a hard drive completely. If you decide to store media on this rig, can always add a HDD later.
Think I'd take Ryan's build, change ram to low profile, add the Evo air cooler, drop the HDD, and get a non-GHz edition GPU and OC it myself given that card's non-reference cooling (or get a Gigabyte Windforce).