goosfrabar,
Well i would suggest u that get that A4 for ur 4 speakers basically front & rear then get another amp to boost ur 12". so i'll check out the price 1st..
my car ecu may need to replace as the engine light is ON when i start the car every morning.
i heard that the replacement with same model will not long lasting, is it possible to change to other model like MMC ecu