My Imac is a few years old (4, I think) and I just had the harddrive replaced 2 months ago after a frightening experience (I thought I had lost everything!) I paid around $450 to have it all taken care of. Now it's back in the shop because of power source issues - keeps cutting off on me. It's out of warranty, and the price tag to have this problem fixed is another $450! Should I repair this thing and pray that it lives, or scrap it and buy a new one? If so, which Mac is best? I am a graphic designer, and use it for print graphics.