ok i've done more homework and i've decided my pioneers are not suitable anymore and neither is the bandpass box they are in. I've narrowed it down to the Infinity kappa perfect 12.1 DVC RMS rating is 350W rms, peak 1400W, Impedance Dual 4 ohm voice coils, recommended Sealed box volume 1.0 cu. ft. im sure most of you experienced guys know that subwoofer, it seems that it gets RAVE reviews all over the internet and over at www.carreview.com it has over 200+ reviews with 5 star ratings making it the #1 rated sub on that website. I did the calculations on my rockford fosgate amp 360 a2 and bridged it will put out 340 rms @ 4 ohms. (listed 170x2@2ohms so formula is 170 * 2 = 340x1@4ohm bridged) correct? so the power is definately ready to be tapped if i wire 2 subs in series to the bridged amp. what i want to know is, my preference is SQL but SPL is not a bad thing either. what is the overall difference between 1 and 2 subs in the sealed box? whats the estimated % increase in SQL and SPL? the car is a 2004 hyundai tiburon which is a hatchback so trunk rattle is not going to be a problem. would i inside the car stand to gain a lot more with that extra sub or is that extra sub more for letting people outside of the car hear your bass... i listen to all kinds of rock mostly .