CPU: i7 920
Motherboard: X58-UD3R (budget),ASUS P6T (mid), X5-UD5 (high end, 3-SLI)
Note: X58-UD3R can do both SLI/CrossFire with a BIOS update.
RAM: Any good brand (OCZ, GSkill, Corsair,etc) DDR3 1333 3*2GB (6GB total)
Case: Antec 900, CM HAF 932, Antec 1200, or any other case you like that has enough space
HDD: 2*640GB in RAID for data
300GB WD Velociraptor for OS
GPU: ATI 4890
Total of that should be about $900-1200 USD or so. With your budget you could spend the rest on a very nice LCD (30" ($800+)or 22-24"($250+) if you don't have space/money).
You may also want to consider a nice water cooling system for the CPU and/or GPU if your interested in that.
edit:
Also get a x64 OS. You can ger the free Win 7 RC and upgrade the OS later this year. Also if you don't have an external back up system spend money on that too.