I just upgraded my studio machine last week to a dell dimension 4600 P4 2.8 GHz, it came with a 40GB 7200Rpm drive and 512MB RAM. I paid $450 for it. Then I bought another gig of RAM and installed my dedicated audio drive. Excellent machine for studio work, very quiet, I have my old P3 800mhz Micron sitting next to it and the fan on that thing is really loud.

Anyway, I run Sonar 3.1 with a bunch of soft synths and it works like a charm, no problems so far. At this price I might get another one for mastering projects. Keep an eye on www.slickdeals.net, dell has been offering their HT P4 based server for less than $400. This is a great machine to built your DAW on.