I bought the two 15" ssx's from 95stroked1500, and I must say I've personally never heard anything as loud - even at the few car shows I've been to. Mine are in a 7 cube box tuned to 32 hz., and the lows are so retarded that you almost can't stand to sit in the truck (chevy suburban). I will say that the higher bass's notes don't really pound, but that's what midbass drivers are for I guess.
My last system was three jl 13w7's ported at 29 hz., and it wasn't as loud as the two treo's! Probably due to the lower tuning, and also the w7's only saw 3000 watts. I'm pushing the treo's with 4000 watts, so I may actually be underpowering the pair, but you'd never know it. I couldn't be happier. You will be satisfied.