Natobasso
Tech-Bot 5000
For what you want to do you sound MUCH better off going with a G4 or G5 Mac. The iMac isn't that expandable or adaptable, but it's benefit is having a small desk footprint and the screen. I have an iMac 17" and I love it, and even though I would like to be able to make mods when I want to it's been nothing but fantastic for me.