Looks pretty good. The HDD may be a bit of overkill, IMO. Get a 74GB Raptor for games and OS, and a 200 GB or smaller at 7200 RPM for media. Also, unless you plan to overclock everything on this build, the 7600 GT might offer you more bang for your buck. However, if you are going to overclock everything, you might want to consider an Opteron 165 over that 3800+. (EDIT: The 165 is dual core too. Slower default clock speed, but if you're overclocking, it doesn't matter.) Opterons are very high quality, and overclock crazy well.
Missing from build: PSU, Case, Optical Drives, OS
EDIT: Also, if you're going to get an Opteron and overclock, you'll want to invest in a good heatsink/fan like the Thermaltake Big Typhoon, and definitely some Arctic Silver 5. A replacement graphics card cooler might help too. Heck, just get some Arctic Silver 5 if you're using nothing but stock cooling. It's good stuff.