Well - in my personal experience a 22" wide screen at 1680x1050 is fine for the 320.
I just played through a couple of levels of FEAR last night because I wanted to test the card overclocked to 635/909 and it ran really smooth with everything maxed and AA at 4x. No hitches or stutters at all.
The overclocking made a HUGE difference in games like Gothic 3 and Oblivion as well. Gothic 3 especially responded great, going from being a little stuttery to basically smooth (minus the area loading stutters, of course)
P.S. - it'll top 80 degrees C but it's definitely worth it.