forgive me for asking this noobish question...but the LCD monitor above says that the recommended resolution is 1600x900...
Wouldn't it matter?
yes it does, first off all the 5xxx ati cards are new so they will be much fassters than the old 4xxx for the same price, they are directx11 compatible the 4xxx are not.
the better the card you get now the longer it will last b4 having to upgrade it later
Hmm... for 1600*900 the 5750 or 5770 are good choices! But as SirKillAlot said. buy the best you can afford, the games in the future are not less demanding... But those two middle range versions mentioned are best in balance with your monitor choice. IMHO.