You will see a drop with a bigger size and resolution, yes. You're not completely out of options, since that is quite a powerful card you will be able to overclock it to compensate. Contrary to what some say, it is a good overclocker and should be able to run stable under 850/1700 @ 1.063. If cooled well enough it will run get stock gtx580 performance if you can get it to 900/2000. Unsure of the voltage requirements for that, however. It will start artifacting if you push it to 925mhz core, so be careful.