I'd say the 2.8 P4 with Hyperthreading, but not the Prescott core, is the best bang for the buck.
And I have to chime in on the MSI mainboards. Mine is an Athlon XP model, but it has been excellent, and I'm happy with other MSI models I've used for my fiancee's machine, and my mom's.
Intel Q9450 @3.2GHz, Gigabyte GA EP45-UD3P, 4 x 2GB G.Skill @4-4-4-12
Antec P160SW case (modded), Xigmatek 750w PSU
3x 500GB (RAID-5), , OptiArc 7200S, ASUS E818A3T
Creative X-Fi XtremeGamer, Hauppauge HVR-1800, Radeon 4890