I have a Late 2006 MBP, with a 2.16GHz Core2Duo, 15" Screen, good hard drive, etc. It's in mint condition (no dings or dents), but it's getting old. The battery doesn't last too long anymore, and I could definitely use a bit more speed. I'm debating between selling it, and purchasing a newer (but used) MBP, or a 13" MBA (new model). Either way, I'd have to spend roughly $500 extra to get what I'd want. On the other hand, I could upgrade the battery to something new (OWC's batteries), and maybe throw in a 256GB SSD drive. Advice?