Ok heres my estimate:
RAM: $450+ for 1000, $250 for 800
Graphics: Last article on X1950XTX said it'd be around 350 euro so i'm sayin anywhere between $450-$550 times by two. When these come out, X1900XTXs will drop in price so you could go two of those if the price is overwhelming.
HD: 2*$250 (150GB Raptor) + $75 (250GB HD)
Sound: $170 (idk wuts a good sound card so u might have to check that)
PSU: $160 (OCZ Gamexstream 700w) $450 for PC Power and Cooling. Here i'd go for the OCZ, its got more power on the 12V rail (4 * 17A compared to 3 * 17A).
RW: 2*$40 (or 2*$60 for lightscribe drives if you wanted them, no use really, i haev one and used it once with the cd that came with it)
Case: anywhere between $50-$250?
Cooling: Tuniq Tower (Really hard to find, dont kno price), Scythe Miner: $45, TT Big Typhoon: $45 Watercooling: go to xtremesystems and look around. FrozenCPU.com has a big selection but a little pricey. This is the kit i was lookin at: http://www.frozencpu.com/ex-wat-76.html
Total: anywhere from $3000-$4500 (estimate, i didnt add them, alot of stuff to add there)