Will Subwoofer Help?

powered subs do take over the heavy lifting from the amp and speakers but in your case I don’t think you need one. From your description of your regular speakers I’m thinking they have good response down to 20 hz. You probably don’t need a sub and if you run the main speakers full range with a sub the sound is going to be way too bass-heavy. Also the sub and the mains will be reproducing the same low frequencies which is a no-no. If you get a sub you want to set a crossover between it and the mains at about 60 0r 80 hz.

m-db, I'm printing out your answer for reference as you've answered a couple additional questions for me. I had forgotten about serial connection for multiple subs. At least  everything is on a dedicated circuit and will so remain. Many thanks.

hombre, this would confirm my initial suspicion. The main speakers are not bass-shy, nor are they terribly sensitive to room placement. My only complaint is that on SOME material the bottom end can sound bloated or boomy. Seems to depend on what is playing rather than something inherent. The subwoofer idea came to me as a way of testing low frequency response with a known, adjustable crossover point on challenging (maybe poorly recorded) material. Actually the mains are rated 22Hz +/- 2dB, and 12" subs rated 18Hz or below, from REL and the like, are not cheap!

Now I'm wondering whether maybe instead I should be looking at tube power amps, something I have always avoided because, one, I'm lazy, and two, even my efficient, sensitive speakers need minimum 20 W. (Though I've read that higher voltage of tube amps obviates any seeming power deficiency). Guess one can always experiment since reputable mfrs/dealers give you up to 45 days to learn whether given a piece meets your particular needs.

Probably the reason some stuff sounds bloated and boomy on the bottom end is the source material. Nothing to do with your system. The best system cannot make poor source material sound good. This is one reason why audiophiles waste a lot of money. They think they can improve the sound of a sh!tty recording. They can't. Unless they get into their time machine and go back and improve the original recording and mastering.

hombre, thank you. Was just hoping for someone to confirm that. Free expert consultation is grand resource. Now I can quit chasing phantoms & go do some detail gardening or rearrange wine bottles. Like maybe everyone, too much dead time on my hands in a lockdown world. Too bad I don't have a novel in me. For once, people have plenty of reading time. 

for some real interesting reading on wikipedia type a search for "Dyatlov Pass incident" and read the article.