Whilst the B&O sound sytem in my A4 Avant is loud and clear sounding, I've always thought it lacking deep bass, that's despite the sub in the spare wheel hole. Being a Bass guitarist, deep notes are the main sounds my ears tune in too, so after some research I opted to install a sub. I've had subs before but this time I wanted something other that just a loud boom-box. Went with th Pioneer TS-WX710A, I've tapped into the existing subs speaker feed and used the 12V supply to the ciggy lighter socket on the right for the subs power-control feed, this powers down when car switched off so is ideal. This leaves a main 15A supply cable to connect up to the battery and its great to have that in the rear already. I strapped it down to the tool kit and using the boot mat from my Skoda, it seems pretty secure. The supplied remote, is nice too, gloss black finish matches the trim perfectly, I've not finished fitting that yet. So, does it sound any good? Oh yeah baby, it sure does and it don't interfere with the existing sound, it just underpins it, no rattles, nothing vibrating, just lovely deep bass added to what was already there.