You might want to consider two screens. Use your existing 19" + a new 24" screen.
It's cheaper than 27"+ screens and you still get more screen real estate. Secondly if you do game, your system better be on hell of a rig to be able to push the FPS for a 30" 2560x1600 screen.
My setup is similar to this guys'. Laptop monitor + vertical 20" monitor.
The vertical monitor is awesome, especially for that white girl or twanger thread!
