I looked at the Totem Kin sub. It is really designed to add some foundation to the Kin mains. At 6”, it is too small to qualify as a sub. The physics just don’t work.

I think you looked at the KIN Mini Sub. The KIN Sub is an 8", stand-alone sub, but I take your point about needing to move enough air. -- Clark2

Subwoofer advice please
 

Correct. I just looked at the Kin Sub with 8” driver.

Same comments apply. The physics still don’t work. No LF is crossover adjustment, and questionable hf outputs for the mains.

This does not meet my minimum requirements for a sub. YMMV and I’m sure some people with very small rooms might be happy with the Kin.