Did you have 12 gigs of RAM with a x32 bit operating system? No wonder you are seeing an improvement. x32 bit OS will only address 4 gigs of RAM. The other 8 gigs was sitting there doing nothing.
KevinDeSmet, what you say is true - to a point only. Smart women and men make parts and assemblies which are efficient, and run as smoothly as possible. However, at a certain point in sheer assembly size, the lack of RAM will catch up to you and lead to crashes and severe slow downs.