Moon harsh? First time I have ever heard those two words in the same sentence when discussing Simaudio.
Yea, my experiences with owning Simaudio also wouldn't have me consider it harsh or bright.
I personally would use the term very detailed and potentially forward compared to some other brands based on the pieces I've owned.
I owned a 600i integrated and thought it was amazing; I found it very detailed, but sweet and smooth. I then purchased Magico S1s and found I wanted a little more power plus a little warmth so went to a Pass Labs X250.8 + Pass Preamp. I found I lost some resolution compared to 600i (but did gain power and warmth) so switched to a SimAudio 740P preamp and it paired with the Pass amp was excellent; my system was very detailed again with a massive soundstage and still that hint of warmth from the big Pass.
I've also owned a 380DSD DAC and I found that not as detailed/forward sounding as a Berkeley and a Bricasti, a more organic meat on the bones type of sound.
I personally think Moon would be generally a great match for Sonus Faber speakers; I could see where some folks may find it too forward with the ultra detailed loudspeakers, but to me that is a matter of taste. My high resolution Magicos didn't reveal any harshness to my ears with my 600i and I still own the 740P.
Cheers