Hate to burst any bubbles here, but a 64 bit OS running 32 bit code does not see much improvement in speed. Once there are more programs written for a 64 bit OS, then yes, speed improvements will be huge.

As al1 seems to be requesting only Dual Xeon 2GHZ and up 1G ram and Up, I cannot post a direct response. One has to remember though, the Management of any Server has more bearing on how well the Server operates, not the size of the engine.