I agree with you about the cost vs mac mini. Last time I checked, Mac Mini's processor only goes to up to 2.66Ghz Core 2 Duo.
Good value for $600 with i3 2.93Ghz with Windows XP or 7 installed will fly like a rocket. Then later, upgrade that to a i5 or i7 for truly a powerful Windows or Hackintosh. I am stoked!