Will adding more ram to my 2.1 20" imac make much difference to the general speed of things? I set it up a couple of days ago, and it feels a little sluggish when i do things, although not brutally slow, i had a feeling coming from pc to mac, that everything would be faster and more intuitive, but at the moment while i am enjoying the mac and finding out new things it can do hour by hour, it frustrates me a little.