After replacing my 2010 13'' MacBook Pro's 4GB RAM with 8GB and HDD with SDD, my computer's performance improved beyond my expectations--what a relief! I'm trying to find out it worth further upgrading my system to Mountain Lion. I got many mixed reviews. If I should, do I really have to buy Snow Leopard first? I really don't want to spend another $20 on something I'm not gonna use. Many thanks in advance.