CPU - Core i7 860 ($275)
MLB - P55-based Mobo with 2xPCIe x16 2.0 slots (Newegg lists $100 to $350 depending on features, though my recommendations fall in the $150-$175 range)
GPU - ATI 5870, no question. ($400-$500 depending on brand and accessories). Save up and get a second one later for XFire.
OS - Win7 64-bit ($150 and up depending on edition - I recommend either Professional or Ultimate)
HSF - Good models run in the $30-$50 range.
CAS - Good ones run about $150 or so.
PSU - Decent 80 Plus Gold 900-1000W PSUs can be had for about $250.
Total, approx 1490, right under budget.
EDIT:
advice from local tech guru Patrthorn
Huh. I'm PatrTho
M, not PatrTho
RN. Never even thought about the possibility of seeing it that way.
EDIT 2: Any of the above figures are subject to revision at a moment's notice depending on whether anybody introduces something awesome 5 minutes after reading this post...or five minutes after that, or after that, etc.
--Patrick