hu bulit in amp question and sub recommendation

[jhnkvn]

im finally upgrading my stock head unit ( 2013 honda city) to pioneer avh 1550. currently i have jbl seps at front and jbl coaxials at back being powered by jbl 640 watts 4 ch amp...since im going to get a HU that has bulit in amp, im planning on having the HU power 1 pair of the speakers ( front or back?) then ill have channel 1 and 2 for the other pair of speakers and have channel 3 and 4 bridged for a 10-12 inch sub...does this make sense? which is better powered by the amp ( and the HU) the front or the back speakers or does it matter at all...finally for my subwoofer issue im not planning on joining any competitions or need a booming setup. just that needed punch to complete the sound experience. should i get a 10 or 12 inch sub, single or dual voice coill? sealed or ported enclosure? please bear in mind the limitation of the amp to be used to power the sub since im not open to purchase another amp just to power a subwoofer...

thanks guys

Front: Separates (Channels 1&2 JBL GT5-A604)
Rear: Coaxial (Head unit)
Sub: Sub (Bridged channels 3&4 JBL GT5-A604)
JBL GT5-12 with 1 cu.ft. sealed box should set you back less than 5,000php.

10 vs 12 - Increasing the displacement only increases the decibel output (around 3dBs) given the same subwoofer model. Other than that, you have to take account linear xmax (google it) and power.

SVC vs DVC - dual voice coils simply allows more creative ways on how to wire the subwoofer. For simplicity sake, just get a SVC 4ohms version. Sound quality stays the same, even if there's an increase in THD, you won't hear it as subwoofers throw out gobs of distortion to begin with.

Sealed vs Ported - generally, sealed needs a smaller enclosure but ported yields a huge decibel boost at its tuning frequency. As you're without an EQ, you can't tame the peak of the ported one.. so stick with sealed.