Power problem with deck?

I recently installed my first system in my truck. I am looking to upgrade some parts of it again but want to make sure I dont run into any problems.
Heres my system: Alpine cda-105 deck, JL audio J2 320.4 amp, x 4 Kicker KS680 speakers, MTX JH600 amp, Kicker L5 12" 2-ohm sub in kicker enclosure, all new kicker wires w/ 4 awg.

Everything works good and I havent gotten around to fully adjusting the amps yet, so the gain on both amps is all the way down. When i tried adjusting the gain, I would turn it up just a little and it sounded like i was overpowering the speakers and sub...and the sub even had a burning smell coming from the port.

I am about to get a new deck, and i am basically set on getting the Kenwood excelon kdc-x994 or the Kenwood kdc-bt954u. Both these decks have 4V preouts for the amps to plug into. My Alpine receiver has 2V preouts and i cant even set the gain on my amps near the 2V setting (the MTX amp has labeled voltage settings around the gain knob) without the system sounding overpowered.
So if I get the Kenwood deck with 4V preouts, do i need to worry about overpowering my system?
There may be another problem in my system, but if i cant really turn up the gain on my amps with the alpine's 2v outputs, what will happen with 4v outputs on a deck?