I built the following box for a friend and I know how this system operates. The build parts were re comended by Brian Yuhas (ranked 53 in the world in OCing). Tons of potential for OCing or years of AHII with no problems. All the parts are from top manufactures and know in the industry. The motherboard is expandable, meaning if you should go TRI SLI you have 3 PCI 2.0 slots not just one no to mention a FSB or native 2000 (depends on memory). NZXT has the quality, fit an finish of a Lian Li case without the cost (I own this case) the E8600 world renown for OCing ability, Mushkin memory is a leader in the OCing world, Tagan power supplies are used in very high end machine builds consistently, eVGA currently the world record holding video card for frame rates in 3DMARK06 and Vantage, I am sure you herd of WD this is a 32MB cache hard drive.
The following system will scream fast. Not hic cup at the furball of 50 persons all seetings to max in the game and still keep 60FPS.
NZXT TEMPEST Crafted Series CS-NT-TEM-B Black Steel / Plastic ATX Mid Tower (110.00)
EVGA 132-YW-E180-A1 LGA 775 NVIDIA nForce 790i SLI ATX Intel Motherboard 8 Phase Digital PWM, 100% Solid State Caps, VDroop Control (330.00)
Intel Core 2 Duo E8600 Wolfdale 3.33GHz 6MB L2 Cache LGA 775 65W Dual-Core Processor (270.00)
Mushkin XP 2GB 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model 99165 (130.00)
ABS Tagan BZ Series BZ900 900W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Modular Active PFC Patent Piperock Modular Power Supply (180.00)
EVGA 896-P3-1260-AR GeForce GTX 260 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card (270.00)
Western Digital Caviar Black WD7501AALS 750GB 7200 RPM SATA 3.0Gb/s Hard Drive (130.00)
LITE-ON 20X DVD±R DVD Burner with LightScribe Black SATA Model iHAS220-08 (30.00)
1450.00 Total and I do giggle at newegg pricing
Optional Fan instead of the Stock fan
OCZ OCZTVEND2 120mm Rifle CPU Cooler (50.00)
1500.00 at Newegg. I can beat the Newegg pricing but not quoting since pricing changes daily
I would get a Monitor, Keyboard, Mouse locally. If you happen to have a microcenter local this weekend they will have monitors on sale 22" LCDs for 99.00 on up