The less money you add to an Ultra the better off you are. Just joking. PO. All you need to do is buy a an amp like you said and the 300w amp is probably over kill for average 6/9's and 6" speakers. 50w/4channels is more like it. $150-$200 at Good Guys, Best Buy, Circuit City and then find out if your stereo has RCA Cables or you may need a high low converter to make it work. $40-$75 max. Then install. Piece of cake.