After many great and faithful years, my G4 Power Mac is starting to squeak and make random chirping sounds... and it is of course very SLOW. I'm afraid it's about done, and I need a replacement. I do part-time graphic design/photography work and use Adobe Creative Suite products. I'm not looking for latest and greatest right now. Looking to spend $500-$800. What can I expect to find in this price range? My instinct is to look for a used MacPro although an iMac might work too.? As you can guess from the fact that I'm still working on a G4, I tend to stretch it as long as I can and from what I have heard, imacs are not as upgradeable.? I'm assuming I'll be looking to CL or ebay and I'd appreciate any advice or warnings about buying this way.