yea... a geo is like a metal box on wheels... so a 10" would do you justice. You get a decent 12" or more in there, and your going to be experincing the rattling that you stated you wish not to have. IMO... in that car, anymore than a 10 is way too much. If it were me.. i would get some nice speakers all around... brands stated above, then get an amp to power them. I wouldnt worry about subs that much. Not being an ***, or implying, but i would just save up to get a bigger/nicer car to put bigger/nicer equipment into. GL