You are running Stable and it's clearly already up to date as far as it goes, i.e no need to upgrade in any way.
Stable itself (as well as the kernel it runs) is fairly old so it wont run nvidia drivers for newer hardware very well.
If you want to have newer drivers you'll need to try one of the Beta versions available, depending on your hardware.
OTH your screeshot resolution looks fine, so why change it? 
