1. If the alternator is putting out more amps than you are using (car & stereo combined) then you will be good, if not you will have to upgrade your alt.
2. IMHO you cannot base speaker decisions on the brand name alone - the only way to compare speakers is to hear them side by side. I like the sound of the Infinity Reference over the Rockford - whatever the top-o-line is, and some people think otherwise.