advice on powering my martin logan vistas

I had Vistas and you do want a lot of power. (I used Anthem then Theta Digital power ampos with mine.) Even though the NAD's numbers are not all that high, NADs have the right power for power hungery speakers. I think you will be fine. I just heard Magnepan 1.7s driven by the same and they sounded wonderful.

BTW, do not overpower Vistas, the panel can take it, but the woofer cannot. IMO the woofer is the achilles heal of the Vista. Great speaker though. Add a sub if you wan more bass.

No, don't use the amp in bridged mode with the Vista. A bridged amp "sees" a load impedance equal to the impedance of the speaker divided by 2. So it would see the Vista's nominal 4 ohm impedance as 2 ohms, and its 1.2 ohm impedance at 20 kHz as 0.6 ohms. The amp undoubtedly would not do well into that heavy a load. Note that the C272 literature only provides a bridged mode power rating for 8 ohm speakers.

In non-bridged mode the C272 appears to be able to provide large amounts of dynamic (short term) power into low impedances, which increases the likelihood that you'll have sufficient power with just the one amp.

Regards,
-- Al

You might have to do some experimenting. I had a pair of SL3's. They should be a bit more difficult to drive than the Vista's. In a medium sized room, listening at normal volumes, I was able to get away with my VAC 30 30 which is rated at 32w /ch with no problems at all. I will say, though, that the VAC is very clean and all but refuses to distort. I would give the NAD a shot first, and use that as a reference if you do decide to upgrade.