I'm a few days away from getting my new Mac Pro and I want to upgrade the ram from 2gb to 4gb. What is the best way to do this? Should I take out the stock 2gb and then add one of those 4gb kits (2x2gb) or should I just add 2gb (2x1gb). When you order the 4gb kit from apple how does it come 2x2gb or 4x1gb?