Screen res question

I have just installed SuSE 10.1 with KDE on a fresh 64-bit machine and would like to increase my screen real estate from 1024 x 768 to something slightly larger. My WinXP machine shares the same monitor via a KVM and drives it happily at 1152 x 864. That being so -- I figure there must be a setting somewhere which will help. It seems to work fine at either 1024 x 768 or 1600 x 1200 (Intel 915G and CTX VL700 monitor) but not 1152 x 864. At that res it squishes the desktop in from the sides. I know I'm being difficult but I'd like to be able to achieve 1152 x 864 which is also 4:3 aspect ratio but more importantly it suits my spectacles prescription very well. Can someone point me in the right direction please. Thanks Mike