basically you can do one of these:
Buy a computer now, and upgrade, and have a BA computer
you can wait another few years for PCI-E and 64-bit apps, and have fun with reinacting the fun we have all had with updating windows for example. oh, and DDR2, which will be compatible with what?... nothing,,, exactly.
you will have to wait even longer for this stuff to be able to be optimized, and fully usable.
get something now, work your *** off for a few summers, then go get your self something nice when PCI-E, and all that other good stuff has been tested, and not so glitchy, and compatible with everything else on you board