As far as subwoofers go, mine came with two 7 inch woofers behind the seats:


(the pair closest to the camera)

A lot of people have discussed putting two 6.5 inch aftermarket drivers in there, but I don't recall hearing about a successful installation. Personally, I don't know how much better aftermarket speakers would do. I took the factory drivers out, and put them in my Grand Cherokee, and it sounds like I have a 10 inch woofer. I have never heard aftermarket 6.5s do the same. They are very very good for OEM.