Do I really need a sub for SQ?
 

Just how it says on title. So far what I have is 2 Cadence ZRS C9 amps,Audison Voce 3 way for front and coaxile for rear and a Bit 1 processor would be running active. This is for a 2012 Challenger.

Absolutely IMO.

You have some fantastic gear already, but your drivers simply won't reproduce low frequencies effectively or provide the intended impact from the music.

Scrap the rears, get 10" versatile sub and you will be set.
You obviously don't crave bass, and are aiming for SQ, so a small quality 10" will suffice.

Personally I'd recommend an IDMax.

have you ever considered 6.5 inch drivers they can produce a good amount of bass for a fraction of the space

Don't get me wrong I do like bass. I had 2 12" p3 subs in a sealed box and a Cadence ZRS C1 amp but sounded too muffled. I guess cause back seat are really thick and cancels a lot of sound.

ive seen that many times , if the back seat wont come down , or doesnt allow some air flow it really makes it hard to get that true bass , have you ever considered putting 8s , or 6.5 inch drivers under your seats ive seen good things from it

what about woofers on rear deck instead of coaxial? was thinking like the CDT,Kicker,Jl audio

ya that would be fine to