67 coupe - Custom Autosound stereo questions

Hi all,

Does anyone here have any experience with Custom Autosound products, specifically the "Back Seat Driver" kit they offer (the rear seat/trunk divider board with the 8" subs and amp).

http://www.casmfg.com/Mustang_Speakers.htm

Anyone used this before? Does it sound okay? I understand with this set up the trunk is the speaker box for the subs but does it make too big of a box? Pretty much everything else is aftermarket stereo-wise. I have been looking for a set up like this that wouldn't sacrifice too much trunk space.

Thanks for your time!

S