I have a Single 12 woofer in my car and I got a single 15 for my room and first i put it in my car and it dosent sound as deep and as clean as the 12. I mean both woofers are very expensive my 12 was 200 bucks and the 15 retailled for 300 but i got it for dirt cheap casue of it being last years model.

the 12 is a ALpine type R
the 15 is a Kicker XPL

ALso the kicker starts poping at higher voulumes. The same happens in the RSX but i have a single 10 comp vr in there.