Pretty solid, but Im not sure if its worth $800.. I replaced an Avatar STU 15 on 3kw with one of these on 8kw, both in boxes designed and built specifically for them, and if this is louder I can't tell. Recently swapped out my Taramps BIG BOSS 8k with a SLAPZ SHOCK 5K.1D and it might actually be louder on the SLAPZ, or at least as loud. Im running a 375a 15v alt with a LiFePo4 starting battery and a 145ah LiFePo4 bank in the back of my Escalade, all OFC 0/1 and 0/2 cables, so Ive definitely got the electrical for both amps. There definitely isn't anything wrong with the Godzilla, but of the many subs Ive gone through so far it definitely doesn't stand out. A good comparison to a more "budget" option would be this is not much louder than two Skar EVL-15s in a 4cu/ft-ish ported box. It doesnt like playing much higher than 80hz tho, which is a bit of a bummer since I havent installed my two 12in dedicated "midbass" (80-140hz or so) drivers so Im not getting much punch from drums and the like, even with four 6.5in mids in each front door.
One thing I CAN safely say about this sub vs others, is it is a power MONSTER. Has yet to let off any odd smells or noises, even when I was running it on 8kw. I do use a Helix DSP.3S for tuning, along with a SMD DD-1+ (sometimes.. I often skip using the DD-1+ because Im lazy), so Im not the local teen with his first car just cranking the gain up till the sub explodes, but still, Ive gone on HOURS long drives with it cranked all the way up on 8kw without a problem. So if you want something that will outlive your vehicle, this is pretty solid. Honestly I am surprised, since my first "real" subwoofer was a XFL-15 and it died after a month on 1.2kw.. Intended on never buying AB again, but when the Godzilla dropped I decided to give them another try.