Radeon HD 6500 lag mouse

[Dan <ganchya@gmail.com>]

Hi,

I bought a brand new computer with a Radeon HD 6500. I installed
debian stable and I have two problems:

The first one is that I am not able to set the maximum resolution that
I have in my monitor which is 1920x1200. I can only set 1600x1200.

The second problem is that sometimes I have a lag of 2second in the mouse.

I guess I have two options. I can install the proprietary drivers (I
want to avoid this option) or I install the new radeon drivers from
backports.

The problem is that if I install the new driver from backports I have
to install the whole new xserver system from backports. Is that a good
idea? In my understanding it is better not install too many things
from backports to have a stable system. What do you think? Will I be
able to get security updates?

Thanks,
Dan