I have one of the first Macbook Pro models and I'm thinking I need an upgrade. It has 1GB RAM, does that mean if I want 2 GB RAM I need to buy 2 1GB and would that be a significant increase in speed and performance? or would buying 2 2GB for a total of 4 GB RAM be the wiser choice? I do graphics and photography and use CS3 the most. Also would appreciate recommendation on HD space as well..