deanx. Go for the touchscreen. I have the 23" Acer and love it. The 27" was a bit over my budget. I'm sure that the 27" will be an improvement over my 23"
It does many things that a knob and fader surface controller could never do, its more monitor real estate , there's no act BS to deal with and it's only going to get better as Cakewalk improves support.
It also rocks if you do stuff other than use Sonar on your PC.