Yeah, they can put the stuff in there for you. I don’t think they carry Fosgate stuff, but the carry MTX and the like. If you want fosgate, go to Best Buy or a local shop that carries that brand and does installs. If it were me, I'd go to a local shop to get anything other than a head unit swap.
I put my amp underneath the passenger seat. I had to take the end caps off, but it fits great and doesn't interfere with the movement of the seat.
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