zsamz is correct. If you want to go faster you will be better off with a P35. If you you want to go even faster still, then get a UT-P45.

A look at the 4.7ghz link in my sig, and you will see 4 sticks of ram running at 563 fsb 24/7 stable.

The ONLY real reason for sticking with the X38/X48 platform, is if you must have 2x16 Pcie lanes. Even then the P45 will run Xfire at 2x8 Pcie lanes, not much of a loss to be honest.