I owned the Sasha series 1s with ARC Ref 150s before my current Alexia 2s with ARC Ref 160 monos. I also had the Sashas in house with the D’Agostino Momentum 250S. I heard them many times at my dealer who often paired them with the Lamm 1.2s.
You can’t go wrong. Note that Marc Mickelson of the Audio Beat uses the Lamm 1.2s with Wilson as his standard system. Many dealers and component manufacturers display Wilson with ARC as do websites--see the French speaker company Triangle’s website and video tours of the Audio Research factory.
So---my subjective impressions:
Lamm is very rich, more bottom up and very refined ,mid-hall presentation. I almost purchased them. There are simply no faults to this amp.
ARC is more transparent, has better highs (but not at all fatiguing) and presents in a very colorful, not colored, manner. Sort of like technicolor on a big screen. The listening seat is more front of the hall and the sound is writ large with tremendous width, depth and layering. The speakers disappear. You can more easily separate each instrument in the mix.
I prefer ARC and especially the Ref 160 monos. But I can also say that the Lamms and even the Ref 160S will do a great job with the Sashas. I would urge you to try to hear both ARC and Lamm--but at least one or the other to know if you can fall in love. If you don’t, look elsewhere.