Hi kjl1065,
First my opinion is your source and electronics are certainly up to the task. That opinion rests on two biases. First over years and several mixes of brands the configuration of a tube preamp driving solid state power amp is in my experience one of the rare hybrids where one gets the best of the two technologies. Second everytime I encounter Bryston power amps the transparency and effortlessness they exhibit impresses.
Now I will humbly invite you to consider my PureArtFi LS-6 as your next speaker. Matt over at Everyday Audiophile does an excellent job relating what the LS-6 is all about in his YouTube review:
PureArtFi LS-6 | Easily one of the best (I've heard)
And more info in this follow-up and our web site:
PureArtFi LS-6 | Follow-up discussion
The reason I believe the LS-6 addresses your desire for "a loudspeaker that sounds rich, full bodied and alive at 50-55 decibel levels." is two fold. First the advances brought by Purifi Audio's USHINDI - Ultra Low Distortion Transducer Technology (USHINDI) set a new state-of-the-art in clarity at all levels including low SPLs thanks to both the lowering of HD & IMD distortions and very advanced magnetic system in drivers' motors. Second the extreme measures we take at PureArtFi in the enclosure design and build quiets the noise most speakers' boxes add to our music.
Feel free to reach out using AudiogoN messaging or pureartfi.com's contact form to discuss this further.