I would love to have a 30 inch personally, but I have 2 24" monitors and they're pretty damn big. I think 30 would be best in your case since they have a higher resolution, giving you more screen space for drawing.
the problem would be, if it's thirty inches, does the pixel count also increase? If you're using a Mac Screen, then yes, it would more than likely pay off, but you pay.... oh you pay... A) Steve Jobs then owns a piece of your soul (it's like stock trading) B) you'll have to pee into two litre bottles and store them under the mammoth desk for your new 30" display because Steve Jobs will take your legs in compensation for the monitor(s).
Oh come on Daniel, how is that true. I mean blatantly Steve would just take the whole soul as well as your arms legs and head and then where would you be?
I would love a 30" monitor, even more so two of them. But, of course, most of us aren't made of money (myself included!), so I' suppose I'll have to settle for two 24"... Someday.
most graphics cards now days support 2 30" easily Nvidia 7600GT+ supports 2560x1600 on both its DVI Outputs and the as for ATI i think the x1900xt+ did/does these are old cards to all new cards support it fine
unless your playing games or doing heavy graphics card work they would be fine