btw KXconfig (in the kde control center, under X) helped me out, before, with the X-setup. I had been trying to get my screen res up to 1024x768, but I was unable to get it higher than 800x600. then I just started KXconfig, changed resolution, restarted - and everything was fine.

seems like you just have to find the right tool... (I tried almost all text-based x-config-programs, and none of them worked!)