It seems to me that you may have pretty much answered your own question....
I have run the KDE and the KDE System Guard, with the XMMS playing a CD Audio Disc, without the Open GL (fancy graphic display) - and it doesn't seem to crash...
This certainly points to OpenGL being the culprit.
Unfortunately it is still true that X crashes more than one might like, and when it does it makes it appear as though the computer is completely unusable.

You would probably find - if you had a second machine connected via a network that you could use to telnet/ssh into the first one - that Linux itself and all the other programs are still running fine, and you could kill off and restart the X server and be on your way again.

When you consider buying your new machine, it may be as well to spend a bit of time investigating video cards, seeing which ones are reported to be well supported, and make sure you get a machine with one of these cards in.