Well as far as using more memory, many programs and windows operations will throtle down if you dont have enough memory. Same in reverse, you add memory, so it uses more to run better, thats pretty normal.
As far as more proccess, i think your imagining that, adding ram alone wont do that.
(By the way, many people, including me, have found that mixing memory brands and sizes can cause performance issues. You may want to consider removing the 128 and sticking with the 512.)