Yes but as of now (until the AMD revisions are released) AMD cannot use DDR2 at all. DDR is the fastest RAM available at the time. DDR2 really doesn't make a huge difference in performance at the time anyway.
Anyway, I'd reccomend going with an AMD Opteron 148 Socket 939 and buying a 6800GS. Take some funding away from your processor and use it to fuel your video card, because if and when you want to game, you'll definetly be glad you bought it. For $100 more the 7800GT provides a whole lot more power, but that will run you $300.