It sounds like your machine probably wasn't capable of running Aero on whatever IGP it had, more than anything. Aero Basic runs excellently on even really old stuff (and handles screen drawing much more intelligently than XP did, so it feels considerably snappier).

6GB sounds excessive for that situation, but if your IGP is getting testy about system memory, it seems likely that it'd require a hell of a lot to simulate decent behavior.

(Typed on my Toshiba Win7 netbook, with a 1.6GHz Atom, 1GB of RAM, and Aero running without a hitch.)