as i posted before i was thinking of installing 2 12" subwoofers in my 98 avalon. however i saw what looked like a stock subwoofer behind the rear seats but still in the main cabin. located right under the rear windshield. does anyone know what size this is and how it sounds after being replaced with a better aftermarket subwoofer. also could i run it from my stock deck if i installed an amp to power it? how would the sound quality be? any input helps.