Box Help for 05 Impala / Vehicle peak?

[Shadow]

I currently have a 2005 Impala and i want to do a custom enclosure for it. Its my family car for now, so the wife still wants to be able to get to the spare and fit a stroller back there.

Currently the car has all stock and factory stuff. I have a Type R 12 in a ported box, that i bought used for 50 bucks. No idea what it is tuned to though.

I am looking into getting 2 DD 1508 8`s and either doing a sealed or t-line enclosure or maybe a horn. That or a 12" FI Q, 12 RE XXX, or a RE MX. I`m upgrading the door speakers with either RE XXX components, or the high end dd components and same for the rear. Not sure which are better though or even if the XXX will drop right in the doors lol.

Sound quality is a huge part to my wife, and I like SQ but want a system that can get really loud. I live in the middle of nowhere in Oklahoma currently, and would like a system that can be heard from a distance if needed.

Currently i have a Kicker SX 650.1 but plan to upgrade if needed. I figured with a tline or horn i would need less power and with the built in DSP this amp would work great with a tline.

I figured someone had to own a 2003-2005 impala and could share what the peak vehicle frequency is, or what enclosures seemed to work best in the car. I have never built a box before, but have had to many prefab boxes sound like shit to go that route again lol. I appreciate any help, and welcome suggestions. Thanks!