Sound quality is hard to judge when you're bass hotspot is far away from your high frequency suite spot so this will be entirely based on the low end reproduction and not how well it blends with the tops (TLAH).
Test setup
Digital (FLAC) audio streamed over HDMI to
AVR 1713 Denon reciever
--TLAH mains (calibrated using audyssey)
--Sub out to --
ART Cleanbox pro -> DCX 2496 -> GX3 (amplifier by QSC) feeding
T60 corner-loaded facing upwards in the opposite corner of where I'm sitting, approximately 7-8 feet.
Back to the review
What it sounds like: A deeper, more extension, version of the T39. It's extremely easy to push this thing to 115 dB measured where my desk is and at no time does the sub-woofer sound strained or slow. I have used a +5 dB boost at the cutoff frequency to attempt at flattening out the response and it does well.
It suffers slightly from the following problem:
Once you start really feeling the bass you get distracted by all the things in the room that are vibrating and what not. Thus the "distortion" in a sense is it will cleanly and without producing any actual THD destroy your room and likely scare your dishes across the house. In my experience I have never gotten bass so clean (at ~120 dB) that instead of the woofer distortion I hear the things on the walls and dresser rattling.
It scares me how easy it is to goose the gain because you don't realize how loud it is until you turn on the SPL meter.
Tests that I like to run for subwoofers:
Podracer scene Star Wars Episode 1 aka the fourth one made
Sebulba (big ugly orange podracer pilot) passing by sounds like a big pulse of air and the low bass is enormous on this section. Brings my MFW 15's to their knees but the T60 is fine with it (properly limited and HP of course)
Music (bass testing music)
Cat daddy - Rejectz Loudest song I testing, very intense, heart stopping loud yet clear
Jokers of the Scene - Baggy Bottom Boys - I'm so glad a forum member posted this song, extremely high volume and high Duty cycle (constant bass)
Tyga - everything he's come out with Lowest bass of the songs I mentioned, not as loud on the low notes (human hearing rolloff) but enough to shake the room
Martin Garrix - Animals Example EDM song, pounds like a concert and then you still have 6 dB headroom

Forum members song (DJ Higgumz) -> getting ziggy ----------- Into at 20-30 Hz makes the whole room vibrate. Dirty 40 Hz Modified sine wave gives you a feeling of panic, and the 70 Hz note hit some extremely high spl.
Actual Music (songs with detailed bass/HI-FI)
I played a couple rock songs, BT, spanish guitar tracks, Glitch Mob/eDIT, and my usual mix up and everything just sounds great, like you take the output of my two MFW 15's at half volume (low distortion) and then crank that up a few knobs. Very accurate e.g. when the bass hits, like a kick drum, it doesn't linger anymore than it is supposed to.
More testing to come when I have a different reference environment.