I'm sorry (dunno why I'm apologizing) but I'm with M5 on this one. SQ is not objective first off, and its judged by ppl who KNOW what SQ sounds like. Im sorry but youre looking for the wrong things. I personally guarantee you (and most of you others) that you don't know what SQ sounds like and would never ever ever ever be willing to sacrifice a bigass expensive woofer like a Q12 for that purpose if you knew. X10 maybe. For any amount of real power, BL all the way. TS specs muddy under thermal duress anyways. Not that most wouldn't be equally happy with one or the other, or could even tell the difference lol. Now I've owned a triple stack Q15 for daily and a plug mag Q12 also for daily. I had SPL BL 12s for SPL (duh) and a BL 15 for bassrace. I now run two BtL N2 12s for daily and bassrace. That's post army, I ran rockford Hx2s and TRFs mostly from 96 and on, with some random JLs and kickers and Soundstream mixed in. I've installed every brand of woofer except DLS and Ground Zero, in most configurations and sizes. With any brand, individual model, size, and power class, you can just as easily have a good result as a bad one, if you are a half-assed type of person. Chances are you couldn't guess the brand of any subwoofer if you were to only hear it playing, so how different can they really be? Obviously there's variability in construction quality, so it makes sense to choose consistent brands like Fi/SSA. Somebody even said you really don't know until you hear it, which is true for 99.9% of car audio. But its up to you to DESIGN the system correctly around the equipment and the space available, budget, etc. If you don't know how to DESIGN a system, you ask stupid questions like "which plays lower?". You can get a 5" midrange to play 5Hz (probably not audibly, but you didn't specify that did you?) its not up to the speaker. When I had a Q15 I had it tuned to like 29Hz in an explorer, and it played plenty low, and loud over almost all frequencies. I did a Q12 sealed in 2 cubes in my wifes jeep and hated the lack of low end produced by the loading direction of the sub. Ported the enclosure and tuned it high, like 36, and i still play down to 25 easy because it loads much better now. My current setup with two BtL 12s plays the loudest on the lows out of all the setups, even with a trunk wall, because my sedan has a long cabin that I take full advantage of. Point I'm making is you have to have goals set and prudent planning to make a great system. Brand names are an after thought. If its going to sound good It's because it was designed properly. End of story. You know what i look for in a woofer? Low Vas. That's what gets me excited. More room for ports baby.