I guess I qualify. I run a pair of Avantgarde Duos which have an integrated powered woofer system that takes a high level signal from a jumper cable from the mid horn. That horn is fed by a pair of Lamm ML 2, which are 18 watts, not exactly flea power, but still SET. (the tweeters also get their signal from a jumper cable from the mid horn). I augment with a pair of subs, 15" sealed box, dialed down fairly low, and have also used the DSpeaker 8033II to help tune the subs. Those are not fed by the SET amp, but are also self-powered and take signal via long interconnects from the line stage. Getting all to cohere took a little time in placement, phase adjustments, crossover point and loudness, but it works and the subs aren't really noticeable unless you turn them off. They do add some foundation to the system and make it sound more spacious. I don't consider the woofers that are part of the Avantgarde to be subs in the true sense, more just woofs.