The Atmas-sphere Class D are GAN amps. I used 2 different GAN amps on m LRS+ and one was adequate, the PeachTree GAN400.The other is a better amp but underpowered for the LRS+, the PeachTree GAN1 (modded).
The AGD and Atmas-sphere, are considered higher end then the PeachTree GAN amps I used. However, I have 2 amps that I think will be to the very top for the LRS+. The Sanders Magtech is exceptional on the LRS+ (used for $4k or less). The CODA #16 is even better. It has a bit more bass.
Yoo need a strong amp for the LRS+ and a bit of warmth is a good fit for me. I owned the Parasound A21+ before but never tried it with the LRS+.I would use that amp if I were on a budget.
Actually, that gives me an idea,