if the amp is 1ohm stable get a dual 2ohm sub, if the amp is 2ohm stable like kickers zx line, get a dual 4 ohm sub. and just wire each sub to its own amp. I would get a massive audio p3000.1. It can do 1500rms x 2 at 1ohm or 3000rms x1 at 2ohms. Theres other amps but its a nice price. its like paying 250ish per amp shipped from low-hz.
it gets full power at 14.4volts. It does 1250rms at 12volts per channel. so I'll break it down.
at 12.4 volts or w/e 1250rms x 2 @ 1ohm 2650rms or so x 1 @ 2 ohms
and then it does 1500rms and 3000rms at 14.4volts. so yeah, its somewhat overrated since it achieves that power at 14.4volts but IMO its still good. Even if it was claimed to be a 2650rms watt amp @ 12.4 volts and does 3000rms @ 14.4 volts is it still not good? IMO its a fairly decent amp. For the price to power ratio its fairly nice.
depending how bigg the batts are and the alt should be able to hold with battery support. I don't see why not. Whats the rated amps at idle on your alt?
Phillp, I have a lot less electrical upgrades than you, and I am always showing 14.4 volts when my car is in motion and 13.8 when it is first cranked up. Also I have 1/0 awg wired throughout my car too, just remember that it give a LOT of juice to whatever it is connected to.