2003 mustang, upgrading system

I have a 2003 Mustang. Currently I have an older high end Alpine head, Kicker KS speakers (5.25 Components and 6x8 Rear) powered by an Alpine V12 5 Channel. That amp also powers an older Alpine E-10 Sub. Its a decent setup but with a 200W Sub, it could use some more low end. I want to add a second amp and replace the sub. Currently the Kicker Solo Classic 10 (4ohm DVC) and a 400-500W RMS (@2ohm) amp is my idea. What I want to know is how to power this. Its currently wired with what I am fairly sure is 8GA power cable. My guess based on this sites charts is 4GA would be sufficient for what should be a total 700 or 800 Watts. Do you think a small CAP would be a worthwhile addition? I initially had a 2Farad cap but it caused all sorts of Alternator whine. Also, if you can think of a good sub (10in) and amp combo with this sort of power and price I'd love suggestions.

alright man. i also have an 03 gt with a similar setup. alpine head combined with a pdx5 and factory speakers. ive done a couple of sub setups. thats a good amp you have man, adding another sub (like the one you have) would let you run that 5th channel at 2 ohms and get the full potential out of it. as far as a cap goes, wouldnt do it. upgrade to 4gauage power and ground and a good battery.weapons of mass distortion

Based on your thoughts, could I just pick up an efficient DVC sub and get the extra power of running a 2 OHMs on the sub channel? Right now the speakers can overwhelm the sub when the system is cranked and the sub channel on the amp is pretty much turned all the way up and on the headunit. I would rather not take up extra space with a second sub and just assume drop a better on in the box (Q-Logic Sealed).

The amp doesn't advertise that 5th channel as stable at 2ohms, plus it would only be like 200W. I think I am going to add an Alpine MRP-M500 Amp and a Kicker Solo Classic 10 (DVC 4ohm). I have a sealed Q-Logic box that the E-10 is in and it should fit the kicker just fine. Will upgrade to 4GA wire for power and ground since I am adding the extra power. Should be a fun little project and add some serious BOOM that the system lacks now.