Have you turned off the program that sets aside ram for programs that is built into vista?
In regards to 6GB of ram, I don't know what the use is for all of that memory, just to have more? I guess that would be the only reason, your not getting a performance increase, just, more space for your cpu to place information of vital programs your running at the time.
Graphic Designers are to blame for this. all the power in the world isn't going to make bad art better. It's about running your programs and things within a comfortable, affordable budget.