if you are absolutely sure that chip supports resolutions higher than 640x480,
just use the best driver you think of the 2, and change the /etc/X11/XF86Config file yourself..
You may have a 32BPP choice that only has a resolution of 640x480.
I would look for a line that states, Default Depth
and change that number 1 lower to 24 or 16.
And if you study the file for a bout 5 minutes you will know how to edit it anyways to your liking.
from terminal type # vi /etc/X11/XF86Config