I've tried the dual 12 setup with a custom box ( 600w type r), Yeah it was "loud" possibly even louder than a single 18. But, if this makes sense, the soundsplinter was felt more than heard ( more cone area) the roof of my car never flexed up and down with 12s. I feel like the 12s were messier due to the fact theres a solid barrier between me and my trunk, so I figured a sealed 18 would give me the tight response and lows I desired ( it did) but zero trunk space and the box bricked my car down more than I originally figured. Im leaning between SSA Xcon series 12 ported, or 15 sealed. I just recieved my tax return so I'll be making a decision most likely by tonight.