I'm gonna get the crap flamed outta me for this but here goes
The cpu i picked will match ANY other in everyday use. There isn't much use for more CPU power when you're on the internet, reading email, downloading "When Horny Animals Attack", whatever. Do you do tons of audio/video processing, gene therapy, or astrophysics? No? Then most of your need for cpu power is video games. It's OK, me too. You won't notice much improvement for spending a lot more money. Retail version - a few bucks more, includes heatsink/fan, 3 year warranty. 939 chip.
The mobo seems to be a solid buy. Asus makes good stuff, and this is a good value because it's reliable and doesn't have tons of stuff you'll never use. On board sound will be OK for now, you can always get a sound card later. It is a 939 - PCI Express board.
The RAM is reliable, cheap, and there's enough of it. DDR400
The nvidia 6600GT cards are a very good bang for the buck. PCI Express to go with the board.
Plextor makes the best optical drives around. You might save a few bucks on another brand.
That's a lot more hard drive for not a lot more money. The speeds should be similar.
Not very familiar with the case, but it looks OK to me. Not super expensive either.
Seasonic makes some rock-solid power supplies. And despite what many people think, you don't need a 25 kW power supply. 350 Watts will be fine for this type of setup.
Poke around these forums. Most questions you have will already be answered.
Good luck!