Monitor res settings problem

Sorry to open a new thread but haven’t found the answer in the old ones.

So I just installed SUSE 11 with KDE 4 but I have a little problem. I use a Samsung 226BW monitor with my ASUS notebook and while the resolution is fine on the notebook’s screen, the Samsung is set to a lower resolution than its native.
I set YaST, activate Dual Head Mode, set the res to 1680x1050 but whatever I do the monitor still has a much lower resolution, maybe around 1280x…
When I set the 1680x the test screen seems to apear in the correct resolution but when it asks me to restart I get this ugly other setting, no matter what I do. :frowning:

Could you help me out?

Generally speaking the resolution depends on the screen size and colour depth .
What is the size of the Samsung 19 inch