Abit, MSI, and Asus is always the way to go. Good thing your getting a 775, rather then 478. I understand you have the 7200rpm dirve for storage, witch is a good idea. But when you have 2 seprate drives working at different speeds at once, rather then togather. You will see a big time difference. If you really wanted to make that system alot better, then dual 74GB 10k drives on Raid would freaking own on that system.
Just think alittle about Raid, it really helps.