Re: biggest monitor I can run with a 8800GTS ?
Well, you could yes, as most people can do it with a 9800GT (8800GTS is better remember). Crysis, World in Conflict etc you very likely wont be able to but if a game lags and its not CPU bound you can just run it at 1680x1050 and youll be hard pressed to see the difference.
But for WoW youre set to fly.
A good 24" is a Benq G2400WD (got mine for $220USD). Also any and all Samsung's that have a 1920x1200 resolution (stay away from the 1080 ones).