Keep the 7300 with printer and scanner you have now. I asume the setup does what you need it to do, so why change.

I don't think those Imacs are very reliable. Sure it might be faster but you would have to get a new printer and scanner and that would cost you money (or time looking on freecycle).

If you are going to replace all the old stuff you might as well get a much newer machine to go with it or don't bother.