[Accord Man]

the least expensive route would be to go with a JBL 600.1.. they are stable down to 1ohms and yield the same amount of power they would at 2ohms, 600w rms)..

Your alternator doesnt have much to do in this.. You simply need to see if you are amp is stable at a given impedance. To help your car's electrical system, you should try to go with power efficient subs (read D class).. The JBL I mentionned is of that type.