to change your resolution the other way, you will have to edit the XF86config-4 file
or use xconfigurator from the console which will do it for you.
To edit the file yourself you; open up /etx/X11/XF86Config-4 in your favorite editor as root. You can open up in the console in vi after doing 'su -' to get into root. or 'alt+F2' to open the run command to run kate (or any editor) then open 'options' and select run as different user and type 'root' and enter the password.
in your XF86Config-4 there is many different sections, the one you want to edit is the 'screen' section. It will look like:
beside 'modes' are the resolution modes your compute can go trhough with <ctrl>+<alt>+<+>
the first mode is default (mine is 1024x768) you can change it to anything you want, just type the res in brackets that you want "1600x1200' for example. Then save and restart X.
To restart X just type init 3 and then init 5 to switch down to runlevel 3 and then back up to runlevel 5 as root. Or logout of kde then <ctrl+e> i think will restart X.