With a proper "big three" you can see little to no voltage drop on a factory alt for a little over 1000rms..I ran a cadence ia9 and ia4 with a factory alt for a bit with minimum voltage drop. although I never got to see it's full potential on that project,I never replaced the factory alt with a HO...Depending of course on the factory alt specs..And the equipment.. But I would always recommend a HO alt if all possible.. The replacement alternators for his car are rated anywhere from 80amps to 120amps. 1000watt amp will draw roughly 70amps--more if you consider the amp isn't 100% efficient, less if you consider impedance. Stock alternators are designed to power the vehicle's electrical needs with little headroom. Even if it drew an average of 50amps that's a large portion of the alternator's output. --- To the OP, Capacitors won't help you. I didn't mention anything about the drivers since I haven't used either. From your post it sounds like you want a driver for output not sound quality--that's not to say it won't sound good, but SQ and "shaking the neighborhood" are polar opposites. Just about any driver sold on this site would suffice. I'm biased as I've only used Fi and SSA, but I couldn't be any happier about their products. I'm not sure how Fi's customer service is these days, but I know SSA is always top notch if that's important to you. I would measure your trunk and figure out how large of an enclosure you can fit / willing to use then depending on that select your driver(s) and size. E.g. an 18" is about half the cost of 2 12"s and the money saved could be used for another battery if needed, etc.