I was searching for 'Sander's and stumbled on this thread.
I own Magnepan 1.7i. I don't own LRS, and I bet that they can benefit from $$$ upstream, too.
Amps I've used with the 1.7i - Pass Labs Aleph 30s, Crown K2, Integra Research RDA7, EVS 1200 by Ric Schultz, Sanders Magtech. The Magtech seems to bring out more bass from Magnepans. Depending on the size of your room, and listening level, you probably will not run into clipping with a Magtech.
I believe Roger Sanders chose to use less speaker protection circuitry in the Magtech, which helps the sound quality. It also has a fully regulated power supply, which helps the amp stay cooler than a class A solid state amp. I found the Sanders sounded better plugged directly into a wall outlet vs. power supply conditioning. (I own an Equi=Tech balanced power unit.)
Changing loudspeakers can be a big deal. I upgraded my Maggie 1.7i with Mye stands, Cardas jumpers, and Cardas spade adapters. Those 'tweaks' were less significant than trying tweeters inside vs. outside, and trying different speaker placement in the room.
I went back and forth reading about crossover mods, and Peter Gunn Magnestand models. If I could audition 'gunned' Maggies locally, I would have given them a shot.
My opinion: See if you can wring out the best performance of your LRS before you move 'up' the Magnepan line. A great amp for the LRS will still be a great amp for a different Magnepan model.