Makiki ride na rin ako since i'm planning for a sound setup din on my CRV... i have some old but never installed gears lying around and probably its time to use them. i would need recommendations though

HU: Currently installed Pioneer AVH-275BT
Amp: JBL GTO 1004
Sub: Polk Audio DXI 104 Dual VC 4ohms (2ps)
Wiring Kit: Kicker PK4 4 AWG Wiring Kit

I am missing seps and sub enclosure and don't even know if the subs and amp would even match... or do i need to buy a mono amp to power the subs... or buy a new sub that can be powered by the existing amp...

budget considerations: i'm not planning to spend a lot probably another 10k for seps including install, sub enclosure and hopefully deadening of the front doors

i'm not going towards loud boom boom setup. just something clear and decent. The back of the CRV is often full due to frequent out of town trips so a small sub enclosure is preferred and I don't have to use both subs i can let go of the other one if needed. Thanks