S-Man
Kinkless Tetrode Admirer
The Kef KC-62 seems to carry a premium price for what it does. SVS, for example, has a similar model for half what the Kef goes for, and other makers do too. At the listening chair, I wonder if 'twice the price' will be audible.
The KC62 has a lot more technology inside. It's smaller and it goes lower. The relevant bit for sound is the LF rolloff - the lower and slower the rolloff the tighter and cleaner the bass will sound... and the better it integrates with the main speakers.
I can program my bass extenders rolloff frequency and despite thinking it would be better to roll off above the main room mode frequency I have found that lower is better. Convincingly better!
This might be worth a look (I'm sure there's a comment somewhere on this site about <14Hz rolloff gives better subjective results):
https://www.rythmikaudio.com/technology.html