That is, for $384 instead of $377 you can have a seriously better CPU and 4 GB of RAM instead of 3, and the MB is still high-quality.
The Q9400 build comes to 145+220+57 for a total of $422, and it's weaker than the $384 Phenom build and has only 3 GB of RAM. I think Intel needs to cut prices on the Q9400 fast...
The HD 4890 is OK. It will even support Havok effects. For example, that scene in the Diablo 3 demo where the barbarian drops a wall on top of a crowd of zombies
I wouldn't bother with the Xigmatek. If you don't overclock, the stock cooler is just as quiet and it doesn't matter that CPU temperatures will be 5 or 10 degrees higher.
Besides, I have no idea if it fits in your case since you didn't say which case you've got.