You don't necessarily need to go the Mac Pro route. At my last job, I had a Mac Pro and it was a fantastic system. I, too, am freelancing full time now and have been using my 2007 iMac without issue. Photoshop, Illustrator and InDesign are just as fast (PS actually starts up much faster for some reason), I have a second monitor connected to it, and the 24" display is greatness.
No, it's not as powerful as the Mac Pro, but since you're not going to be doing video work, you may not ever experience a lot of that power, anyway. If you can hold off a month or so, there will probably be a new version of the iMac.
As to your question about the Adobe programs, PC vs. Mac, I can honestly say there isn't a whole lot of difference. The only real difference I've ever noticed is that on a Mac you use the command key for the major keyboard shortcuts instead of the the control key. Really. That's the only difference.
No, it's not as powerful as the Mac Pro, but since you're not going to be doing video work, you may not ever experience a lot of that power, anyway. If you can hold off a month or so, there will probably be a new version of the iMac.
As to your question about the Adobe programs, PC vs. Mac, I can honestly say there isn't a whole lot of difference. The only real difference I've ever noticed is that on a Mac you use the command key for the major keyboard shortcuts instead of the the control key. Really. That's the only difference.