Re: Moving to a single 15
^^^ This.... Part of the way to get higher SPL numbers is by tuning your box closer to the tone you are trying to hit with. Low tuning and low tones take lots of power and cone area to make high numbers. Higher tuning and higher tones take less power and cone area, in general...
With 2500RMS and 2 12's.....you should easily be doing in the mid 140's by now. I have about 1000 going to my 2 old *** PG subs and I'm in the low 140's and tuned to 31hz.
'65 VW Bus
(2) PG Ti 12's, (2) Aura Sound 8's, (2) SoundStream 6.5 coax, (2) Alpine Type-S 6x9's [rear fill], MBQ DSC1500.1D, RF 501X
'02 BMW 330xi (AWD coupe)
Harman/Kardon 12-speaker System Option - sounds good =)