Want a 2010 8-core Mac Pro running at 3.46 GHz? You can have one now. (2009 models are still limited to 3.33 GHz 4-core).
The upgrade isn’t cheap (Intel Xeon CPUs are very expensive), but if you must have the fastest thing, it’s now an option.
An 8-core at 3.46 GHz is a near optimal solution: fastest clock speed and 8 cores serves just about any need. A 12-core 3.46 GHz is a great option also, but will cost even more (available soon), and will be useful mainly for specialized software.
More options are coming within a few weeks, including 6 cores at 3.46 GHz, and 12 cores at 3.46 GHz.
Of course, such upgrade are best done up as an MPG Pro Workstation, because without the right drives and memory, a fast CPU will stall.
2009 Mac Pro
Upgrades for the 4-core model.
Upgrades for the 8-core model.