I would definitely recommend a P4 C and an Intel 865 mobo.
I have built several using the Albatron 865 PE Pro mobo and various speeds on the P4, and I've been very pleased with the results. You can get a 2.6 Ghz P4 C from ZipZoomFly.com for $209, and the Albatron mobo for $95.
I run ultra-quiet with a Nexus Real Silent 300W power supply (under 20db), and a Zalman CNPS7000 cpu fan ($69 and $29 at EndPCNoise.com, respectively).
I'm running 2 striped Seagate 60 Gb SATA drives, a Radeon 9000 Pro, and 1.5 Gb of Kingston HyperX.
Just my two cents...
Sorry for the double post!