which one would thump harder? im talking like the same total rms.

ie: 700 RMS on the 15" or 350 RMS each on the 12's

 

the 12s

 

2 12's

 

the 15 will hit lower and harder than a 12 but the 2 12's will sound better in the long run

 

/\ agreed

 

depends on the music you listen to.

15 is good for mostly rap. if you like differnt genre's, I'd stick with two 12's.

 

12's

 

The 2 12's would hit harder from the overall greater air displacement.

I don't see how they'd sound better "in the long run." This is one of the biggest myths in car audio. Read: Mythbuster #2- "Large cone subs don't sound as good as small cone subs."

 

yes. the 12s.

 

It takes more power to move more air. You must match the power to the speaker. In theory a properly powered 15 should sound good as anything although I have never heard one that didn't sound like crap. the 15's do not hit any lower than my polk 12's (20hz) but they do move more air.