I take it you want to keep you current video card?
Then the P4P800 would be a good choice. If you were looking to upgrade the video card also, you might look at the P5GDC.
Mushkin ram is one of the best.
As far as changing mother boards and keeping the old drive.
Microsoft Motherboard replacement
http://support.microsoft.com/default...b;en-us;824125
Happy Thanks Giving