Amplifier design parameters required for a good match for high (16+) ohm speakers?

Ralph,
I find the paring of the Contrasts with the ST-70 to be quite adequate in my 12'x15' acoustically treated room. Bass has improved with playing time. The Contrast are certainly revealing such that for my tastes best mated to warmish SS or tube amplification. It was their 16 ohm impedance that drew me toward the purchase. 

Regarding the mono mode question: I am asking about your experience using two ST-70s as mono amps. I believe this is strapping.  Based on the owners manual this can be done.  

Forgot to add that the manufactures rated sensitivity was based on 1 watt, not 2.83V.  This is what seems consistent with the loudness I obtain when comparing to other 8 ohm speakers having 88-89dB sensitivity at 2.83V.  My assessment is based on comparison with equal volume setting on different preamps, integrated amps. Not a true measurement. Again, I was more concerned about the impedance factor than the sensitivity as I have a small listening room and listen in a near-field environment.

Forgot to add that the manufactures rated sensitivity was based on 1 watt, not 2.83V.

@mesch
In that case 'sensitivity' is not the right word- 'efficiency' is.
IME monostrapping the ST-70 is easy and works quite well.

Thanks Ralph! As it turns out, I may become an owner of another ST-70. Same vintage as the one I had you refurbish in spring of 2016. I will be giving you a call regarding doing same work on it should ownership happen.