Hey guys bought a ba xt last week, i have a mono block a 2 12" subs from my previous car that i want to install.

I want to run the stock head unit just because i dont want to put an aftermarket one in and make the stock one redundant i like the steering controls.

Been told cant add sub to stock if i do i will only have two speakers not 4.

Could i put an aftermarket one in and run the stock player to the aftermarket as an aux input or something?

Need some help people