The best chips available on the Market right now, are the new Barcelona core Opterons.

They win hands down. HyperTransport 3.0 eliminates pretty much all the FSB Bottlenecks, You can have upto 8 CPU's on a single motherboard (thats 32!! cores). With DDR3 about to make inroads into the memory market in a BIG way, Opterons are looking like the chips that'll get the most out of it.