Don't get a 30" monitor! I forever regret the one I got. It's difficult to find a good layout for 5 accounts that looks good and when you are not playing WoW your web browsing experience is shit. Having a 30" window of a webpage is super lame in the looks dept so I would reduce the size of the window. Well that left me with a 3" border around the window and you can't use that space for anything. Don't do it! I bought 2 24" monitors and wish I had done so from the start. Also 30" monitors will be rough on your GPUs (I had a 3G 580 at the time) if you are doing another monitor in the setup. I couldn't get all the eye candy on all 5 accounts and run another smaller monitor off the card for web browsing.

Looking back I would probably do 3 or 4 good computers with 6 monitors and all the eye candy you can handle in WoW, but I just don't have that kind of space in my house.