I inherited a mid-2009 Macbook Pro w/2GB RAM. I want to upgrade it to 4GB. I understand that the best performance is achieved with matched RAM. I have read some forums that imply that unmatched RAM will suffer a 10-15% performance degradation. Here's my question: Would overall performance be better if I buy 1 4GB RAM, and pair it with a ! GB already in there (giving me a total of 5G)? Or, should I remove both, and buy 2 2GB (for a total of 4GB). Which choice is better overall? (The machine is used primarily for web surfing, watching videos, and some financial applications with real-time charts/graphs).