I have a 15" iiyama flat-panel display connected to acomputer with a ATI Rage Pro Graphics board and I have found it to work well with Debian RedHat and Slackware, For the moment I have both Windows and RedHat 6.1 running on that box and if I remember correctly the accelerated server to use is Mach 64. As far as I can remember you can choose flat-panel during the xfree86- setup. Thats what I did.
I may sound vague but I tend to forget these things but from your setup you really shouldn´t have any trouble. Should you get into trouble I can mail you my xfree86config for reference. Beware of copying straight of. Jonas Anderson