To my knowledge, The Adobe suite is mathematical based, so they rely more on processor than GPU requirements. All your vectors, masks, filters, and so-on rely on the processor to compile them as visual effects..
not since CS3. CS5 relies more on GPU for processing and DEFINITELY for display.
Get an iMac or comparable PC for cheaper. Yeah, I said PC. You don't *need* a Mac for development. I could understand if it's a *want*, which is why iMac would be a better choice. I would also wait a month or two to see if any rumors about a standard iMac speed bump w/Sandy Bridge procs will be introduced. Since Apple doesn't lower their prices on their current (aka year old) models, you'd do wise to wait to see how things shake out with any new refresh.