I'm in the market for a new 15" 2.4Ghz MBP, and I'm trying to decide which of two potential deals would be best: 1. Buy it with an upgrade to 4gb RAM for $1800. 2. Trade-in my current computer (15" Pbook) and get $500 towards the purchase of the new MBP priced at $1967 (without the upgraded RAM). Any thoughts on which way to go?