[Shinigami]

If you go with Xeon's, you'll be paying quite a bit of cash... not really worth it if all that you're looking for is an answer to your curiosity.

Also, many Xeon boards don't offer the chance to hook up proper video cards to harness all that power.

I've been running SMP PC's for a long time now, and whilst they're nice when you have a certain number of applications open (for example, surfing the new while rebuilding a 3d scene is no problem), you need to understand that there are many applications which simply will not take advantage of multiple processors. Games are notorious for this, and those who do support more then one processors, don't usually run that much faster as the bottle neck is often the video card, and it also requires some tinkering to modify the game to run that way...

If you want SMP, just go with a dual AMD system or something. Not too expensive, and you'll see some difference for sure.