I would suggest the G5. Granted, money may be an issue. But whenever people say a computer will be "good enough" for this or "just fine" for that, just remember, sometimes even on the smallest things, such as word processing or emailing at the same time, to have a faster computer means absolutely no lag time. That goes for applications loading, files opening, audio streaming, videos rendering, photo manipulation and effects (you even said you'd be using photoshop), and you'd have your bases covered for the occassional game, should you decide to play one. Which can sometimes make computer a whole heck of a lot easier and more enjoyable.

To put it in a nutshell, get the best computer you can afford, and not what you "think" will be all you'll need it for, cause you'll end up getting an underpowered computer and kick yourself in the butt later asking yourself why.