So its is turning into mac vs the rest.
Back on topic.
The cheapest iMac will do the trick for your needs easily. I agree with paul13walnut5 that getting a ssd or fusion is the bigger difference.
Just got the mini i7 and have Apple put in the ssd(256) and working with Aperture and Photoshop its really fast. At least compared to my old iMac - 2006 model.
I later put in 16gb of ram, makes it smoother but the ssd is the wow factor.
Of course if you get an iMac you have a better graphic card and with an update of ram and possibly a ssd or fusion drive you will be needing a safety belt and crash helmet.