I have heard the Peerless XLS subs. It really is a great sub. But I'm not sure if it will produce the SPL you may need. I am also looking in to the subs. All I need is a 135db score and I would be sold.

 

I have them with 501bd fosgate which is 500 watts in 2 ohms,haven't checked how loud on a rta but pretty sure it would hit 135db.The 12" is 94db 1 watt meter in efficency

 

My Vifa can easily hit 135. My amp is badly clipping, and in a SQ box, and i still did 131. the Vifa is 97 db/watt/meter. So its crazy effecient for a car audio sub. It sounds........ unbelieveable, Im extermely happy with it, I'll never buy another sub again. The cool part is, I can get a new one, in a built-to-exact-spec pro. made SQ box for $200 CAD.