Will Subwoofer Help?

Thanks, miller & ozzy. I guess just start out running everything full-range, then tweak crossover if/as needed. Think I've got tower placement figured out, and from what I have read, sub placement doesn't really matter. Though I would start between, which seems both convenient and logical.

Would the overlap in the sub-100Hz range add clarity rather than just augmentation? I have read that removing the deep bottom from the stereo pair allows the amp to sound better in the mid-bass and up. Although mine (Class A/AB) doesn't get all that hot even at 90db SPL. At least not in winter . . .

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.

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. 

"The events of the past, through lapse of time, have fought their way, past credence, into the country of myth." -- Thucydides