For one, you shouldn’t need to ask anyone which amp you preferred the sound of! You did the demos; you should have a good idea of how these amps performed respectively with soundstaging and separation.
Second, it’s odd that you compare amps of such different price brackets, but also will not consider anything else in that range, e.g. if you like Naim, why not also demo Naim components of equal value to the Simaudio?
Third, if your real quesiton is the ability of the Supernait to drive the Contours, well again, you did the demo! Did they sound like they were clipping at high volume? Did it run out of headroom at high volume? Did you hear distortion in the speakers? Did the amp go into shutdown mode after some short period of time? Did the Simaudio have a better sense of control and ease of listening compared to the Naim? Do you even listen at very high volume? What distance are your speakers from your couch?
Crudely, if you sit up to 3 meters away (9-10db loss), you’d need 58w to hit 100db for these speakers (the same volume as a jack-hammer!). Supernait 3 shows 130w into 4ohms, so should have more than enough "power", assuming the amp is able to deliver the required current without distortion or thermal shutdown.
