A friend is a longtime Atma-Sphere owner and I am familiar with his MA-1 mono blocks. So I feel that I can extrapolate the sound of your M-60 mono blocks. We paired his MP-1 preamplifier with my Frankensteins and result was pure and gorgeous.
I can easily imagine your CSL and M-60 pairing being every bit as accomplished. Ralph has described his OTLs as 3rd order harmonics signature and SET as 2nd order harmonic signature. He is spot on with this distinction. He pointed out that naturally a listener may prefer one over the other’s presentation. Bottom line is either is quite capable of exquisite sound quality with proper set up.
Bill your former Coincident Triumphs were very easy to drive just like my Total Eclipse. In fact I believe that the old Eclipse series of Coincident speakers were probably the most compatible with SET amplifiers. 14 ohm load impedance will do that.😊
Charles