decibels

here's the deal. i have a FI Q 18 in about 5 cubes sealed in my scion tc. running off of a Cadence Dakota 2400 maxx...1200 rms @ 1 ohm amp. Today we metered it and I got about 138.9 dbs...which isnt horrible but definitely isnt good. I want to get to around 150dbs. Someone suggest a bass...