I'm going to get a 13" MBA for college. I was going to get the base model with the 4GB upgrade, since I already have a 21.5" iMac for my main machine. But my mom posed an offer to buy my iMac off of me...should I upgrade to the ultimate 13", get an external HD and sell the iMac? I have a 32" tv I can use as an external monitor for movies and such. I do photography and play games, but nothing I couldn't stash on my external HD. I'm just worried I'm going to miss my iMac...it's a powerful, fast machine and has been my baby for the past year. Thoughts?