I dunno, I'm on a somewhat limited budget. The 12" Type R's would be the cheapest way to go, but how much louder would the 15" Type R's be than the 12"? Also, what size box would I build for the 12's and 15's, like a 6.8 cubic foot for the 12's tuned to 36hz? I've never dealt with these subs, but my goal is to have insane midbass that's hard to breathe, but also some sick low ends.