http://www.thesafehouse.org/kb.php?m...ticle&k=20
Ruccus makes some good points in that. There's a lot of uncertainty about things right now. I'd probably either wait for things to stabilize a bit, or buy something really cheap (which can still be decent). It will depend a lot on what you have now too. If you're on a P2-350MHz, I wouldn't give the same recommendation as if you were on a P4-2.0GHz.
Like Martard said, my general belief is that you should upgrade when your current system isn't doing what you need it to. I don't recommend buying hardware to go with stuff that hasn't been released yet. Specs change, delays happen, etc. Nothing like spending all your money to get the best, only to find out that it isn't actually the best when things are actually released...