For a strickly folding rig, I would say go with a inexpensive P35 chipset motherboard. I need to do some research to see how the G33 chipsets are overclocking the quads, because if they can get you to 3.2 - 3.4, they have a great price.
What you dont want to do is try to save a few dollars on the HSF. The quads do produce more heat than the C2D. This can reduce your OC, as well as stability, so something like a Ultra 120 or Tuniq Tower.