1 x Intel Core 2 Quad Q6600 Quad Core Processor LGA775 Kentsfield 2.40GHZ 1066FSB 8MB Retail Box
This seems like overkill for gaming - most games don't make use of multiple cores well anyhow. Possibly it has value for 3D rendering, but this is not my area of expertise.
1 x ASUS P5N32-E SLI Plus ATX LGA775 DDR2 Nforce 650I + 570 SLI 3PCI-E16 PCI-E1 2PCI SATA2 Motherboard
Seems fine, bonus points for not having one of those evil 40mm NB fans.
1 x Arctic Cooling Freezer 7 Pro LGA775 2500RPM 45CFM
I am agnostic on coolers and thermal paste. I only buy super quiet/fanless ones myself but silence is my fetish, not yours.
2 x OCZ ATI Crossfire PC2-6400 2GB 2X1GB DDR2-800 CL5-5-5-15 240PIN DIMM Dual Channel Memory Kit
4GB of RAM (if I am reading this correctly) is a complete and total waste on any windows based system. The system is going to reserve most of the addresses past the 2GB space for the video card and system functions, so you'll never see the last 1.5GB
1 x EVGA E-GEFORCE 8800GTS 500MHZ 320MB 1.6GHZ GDDR3 PCI-E Dual DVI-I HDTV HDCP DIRECTX10 Video Card
Why not a GTX? Spend more on the graphics card than anything else, that is what will keep your system current enough to play the new games for as long as possible. This doesn't mean you should spend double for a 5% performance boost though.
1 x Antec Sonata III Black ATX 16IN Mid Tower Quiet Case 3X5.25 2X3.5 4X3.5IN 500W 120MM Fan
I love Antec cases. I prefer the P180 line to the Sonata line, but again I am a silence nut.
1 x Seagate Barracuda 7200.10 320GB SATA2 3GB/S 7200RPM 16MB Cache NCQ Hard Drive
1 x Creative Labs Sound Blaster X-FI Xtreme Gamer 24BIT Sound Card 7.1 PCI Retail Box Bilingual
These seem fine
1 x BFG PhysX Card Ageia Physics Processor Card PCI 128MB 128-BIT GDDR3
I'm a bit dubious about this - never read a good review of these. Seems like the money could be better spent elsewhere.
EDIT: Make sure to post a source link and/or price, it'd help me out a lot.
I already have two 19" LG monitors, a G15 keyboard, and a optical microsoft mouse.