I am having difficulty making artwork on Photoshop CS2 and Painter IX because with 1200 X 1800 Pixels it runs too slow and I heard this is the best size for professional work (I'm not saying 'I' am, but I would like to work at what they do). My system is as follows:

GeForce 6600GT 128bit
1024 RAM
3.2 Celaron CPU (getting this was bad as it made my gaming unplayable).

I might buy a new CPU, which would be best for performance?