Are the processors in the Mac Pro upgradeable, or are they a permanent part of the motherboard? I ask because, if there's no upgrading the processor in the future, I may as well get an iMac.

The processors are all "upgradable" in the sense that you can pull them from the sockets (in all the systems, not just MacPros). But often the next gen processors use new sockets or chipsets or memory, so you won't have upgradability over a long period of time. Upgrading the processor is not officially supported by Apple, but it has been done for years (I have 2 Cubes, one at 1.25 Ghz and another at 1.7, both were 450 Mhz machines). I have read of a number of people upgrading MacPros as well.

Unless you're comfortable with playing with heat sinks and heat transfer paste, you should have the upgrade done by a professional.

Thanks, Jack. I did the same as you with your Cubes- upgrading my G4 500MHz to a 1.4GHz. I was hoping that in the future, as NewerTech did, someone would have a noticeable speed increase, in a compatible processor. That G4 "bump" helped me when I wasn't able to get a newer CPU.