Actually you can run photoshop on Dell M6400 i7 duel core 2.66 GHz.
I got my cintiq and I am planning to buy that along with other junky stuff like Photoshop CS5 and so on.
EDIT: Make the following.
-Photoshop CS 5
-Paint Tool SAI
-Zbrush
-Sculptris
-SoftimageXSI
-VisualStudio.NET
and so on with no lag issues or crash issues.