I was running a 7900gs on mt 22" monitor, and really I would not recommend it for anything higher than 1280 x 1024.
Yes, it will run all CURRENT games fine, but some of them only just. F.E.A.R for example is ok in single player, but multiplayer the card takes abit of a knock at 1680 x 1050. Oblivion is playable, but depends on how fussy you are about settings.
for 1680 x 1050 (and it really is best to run monitors using their native res) I would not recommend anything less than a x1950xtx. Lets face it, people who splash out on 22" monitors should not really be holding back on their GPU.