Loopee,
I have a LMIII and a SL600. The LM is effectively now a back up amp. But they are both similar in tone (warm), the SL just has more of it. The SL goes lower and I like the mids better, I think they are more balanced with the voicing. The highs are more natural to me, and not overbearing when boosted. I think the mention above about wanting to punch ,instead of cut, through and wrap the music is a great idea of what the SL will do/can do. YMMV
I have a LMIII and a SL600. The LM is effectively now a back up amp. But they are both similar in tone (warm), the SL just has more of it. The SL goes lower and I like the mids better, I think they are more balanced with the voicing. The highs are more natural to me, and not overbearing when boosted. I think the mention above about wanting to punch ,instead of cut, through and wrap the music is a great idea of what the SL will do/can do. YMMV

