Hi Bigtwin! Good to see you over here. Congrats on your SLs.
Couple things-
First, Roger West is pretty responsive to questions. Ususally responds to email next day. I peppered him with questions about subwoofer crossover, speaker setup in my difficult room, and more. In the process I found out Roger listens to Benchmark ABH2s. He uses two as monoblocks. Gets his highest recommendation.
Second, my SLs are preowned M1s with upgraded backplates that I got last August. My experience has been that, like the Quad63s they replaced, you need power. Both the Quads and SLs will suck dry either a McIntosh MC352 or MC2500. I use a subwoofer to handle much of the lower frequency load, trying different crossover frequencies right now. I like to listen to jazz/pop/funk 80-85 dB with tops 90 dB peaks. Classical music peaks around 80 dB tops live. So your Mahler is easier to handle.
My panels are 20 years old but in excellent shape. But they don’t have the Bass Focus feature and maybe other upgrades. So YMMV.
Will be interested in your report. FWIW, my wife, who has been agnostic about my audio purchases over the years, thanked me for buying the SLs.