yea i would say 24+" is your best bet. There is a samsung 24" i saw in costco around 300. But if you managed to scrounge up an extra 200 you can get yourself the HannsG 28" 1920x1200. I got one when it was 680 on newegg about 10 months ago. Best purchase I ever made. I dont think I can ever go back to anything with a resolution below 1920x1200.
With the card you have, (better than my 8800gt) you should be able to reap the 1920x1200 beauty in games. I can handle most games like Doom3, HL2, CSS, TF2 with max settings and anti-alaising at this resolution.
I wouldn't settle for anything less than 1920x1200 imo.