As Ivan said, and Mac mentions in another thread... the Growlers aren't in the same market/class as BassMaxx, Danley, or some of the others... What Jeff's little sub does is go lower, louder, than similarly priced and positioned products, and it sounds better in the process.
That is why the Growler got into the listening tests at the NYC Sub shoot. It stood out. We passed over the EV Phoenix sub, the l'Acoustics SB218, and a couple of others after hearing them do the TEF sweeps. While the Growler might not "out-perform" either of those examples, for what it is, and what it costs, it's an exceptional performer/value for those who's needs can be met by it.
If our corporate biz works out, I'd like to have 4 or 8 of these to hide behind silk plants when the decorator has final say on sound placement.
Have fun, good luck.
Tim Mc