So here's the story. When my local CompUSA closed down I was able to buy their remaining stock of Mac Pro 2.66 Quad-Cores at a good discount. The plan was that I would sell all but one of the new-in-box systems and my dad was going to buy the demo unit. I will make enough money from the systems sold to make the one I keep essentially free for me and I even stand to make a couple hundred bucks on the deal. Well, my dad decided that he's fine with his iMac and said to go ahead and sell his system too. I have been using it while I sold my remaining stock before I opened up "my system" and sent this one to my dad (at his suggestion), but now I am not sure what to do. Should I just keep using the demo unit (it works perfectly, and is not beat up at all, but I don't know how long it had been the demo) and sell "my system" or keep "my system" and sell the demo? Obviously, I make more money selling the new unit, but the newness of "my system" is tempting, too. What would you do in my situation?