I'm going to have to disagree with Otis in this case.
For a $2000 budget you could easily go for the $320 i7 920 processor. It is equal or greater in performance to the $1300 Q9770 and the X58 platform has proven to work extremely well with SLI and Crossfire solutions.
Thermalright Ultra 120 is the king of air coolers right now. Go for it (I know I am ;D)
If you are getting the Cosmos, get the S version. Better features, better cooling and much better appearance.
Also, if you can, get the older GTX 260 as it is $80-$90 cheaper right now and is only 1-2 FPS behind the Core 216 version. It was really a pathetic move from Nvidia to release the 216 version.
Really though, for $2000 you should be aiming for the 4870x2. The best single GPU on the market; more powerful than the GTX 280. Crushes any game. It could be yours for only $550 :D