well if price is a concern then check out this thread by dr zero:
http://forum.arcadecontrols.com/index.php?topic=94657.0the price is pretty good for a still pretty capable system.
DO NOT buy a phenom processor, they are the sux, the phenom II however is'nt bad.
if you've got enough parts to salvage then i'd say go with either a intel e5200, or a phenom II x2 550
both those go for less then 100 bucks, and boht over clock pretty well.
a mother board should be easily had for less then 100, there are better deals to be had on the intel 775 boards, i've seen some nice gigabytes go for like 40 bucks AR lately.
micro center had one about 3 weeks ago.
if you dont care about over clocking i can recommend going with ECS boards, they're pretty no frills, but all the ones i've had been rock solid stable and are cheap.. usually under 50 bucks even when not on sell.