I had built a box for a 15 HDC3 but had a kicker cvx 15 in temporary, built 16H, 34W, 32D and 8" Port about 5^ft and tuned to 33Hz. Thing got LOW and LOUD!! I loved it! but I sold the Kicker and the box to a friend of mine. I think im going to seal box from trunk, subs and port firing forward, tuned to 34hz on 2000rms. Even still the idea of a 4th order in a Cavalier all Trunk Setup keeps repeating in my mind. Do you think a 4th can be done with 2 SDC2.5 12's?