I like to use Cyberpower (
www.cyberpowerpc.com) as a reference. I've found that using Newegg for parts, it generally ends up pretty close just pricing the system out from them.
I really like the 8800 GTS (which is what I currently own) and also recommend the Penryn series (latest Intel Core 2) CPU. I chose the 2.66GHz below for its optimal price point, but going up to the 3GHz is not too much more. You can fiddle around with motherboards but I think ASUS does a really good basic SLI ready mobo. With this system you should easily be able to handle any game out there right now at close to max details. Crysis may not run 100% maxxed out, but it will be close.
I put together a modest recommendation for about $1000 (no monitor):
$1017.00
CASE: ($10 off Mail-in Rebate) Raidmax Sagitta II Mid-Tower 420W Gaming Case w/ Side-Panel Window (Black Color)
CPU: (Sckt775)Intel® Core™ 2 Duo E6750 CPU @ 2.66GHz 1333FSB 4MB L2 Cache 64-bit
MOTHERBOARD: Asus P5N-E nForce 650i SLI Chipset LGA775 FSB1333 DDR2 Mainboard
MEMORY: (Req.DDR2 MainBoard)2GB (2x1GB) PC6400 DDR2/800 Dual Channel Memory (Mushkin or Major Brand)
VIDEO CARD: NVIDIA GeForce 8800 GTS 512MB 16X PCI Express (Major Brand Powered by NVIDIA)
HARD DRIVE: Single Hard Drive (500GB SATA-II 3.0Gb/s 16MB Cache 7200RPM HDD)
Optical Drive: (Special Price) 20X DVD±R/±RW + CD-R/RW DRIVE DUAL LAYER (BLACK COLOR)
SOUND: 3D WAVE ON-BOARD 5.1 SOUND CARD
Power supply was upped to a 500W one, not sure why it didn't show up.