You'd need a good monitor (IPS or better, [link]).
You'll also need to calibrate it properly if you're super serious about colour. Either with calibration software or hardware (hardware like Spyder 3 can cost $250), or calibrating it yourself (which can be inaccurate if you don't know what you're doing.
do you get any colour banding with your U2311 at all? you know what i mean right? its really noticeable on my £150 lg....i thought my HDMI lead was a good one and Ive not tried a different one so it could be that I suppose...but then again i think it is time for a pro monitor... and yeh i play games too sometimes so it will be nice to have a dual monitor setup