In my opinion, the X48 motherboard might be overkill depending on how far you're planning to OC the machine (and you should only be considering it if you're going to OC). With a 9X multiplier you won't have to push the FSB too hard to get satisfactory speeds, so you might even consider a P35 board for a fraction of the cost. Also look into getting an aftermarket cooler.
X48 is basically a little updated version of the X38 that's been officially certified to run at 1600 fsb although everyone knows that they could run that fast a while ago.
