If you are spending Nagra money the KRELL KSA i400 would be what I would look at. I have owned 2 of the lower end models and they sounded great. Super smooth and buttery sound with good detail. Class A using the KRELL iBias system. It also runs cool.
Th KSA i400 is much better than what I owned (K-300i and Duo 175XD) and can drive any speaker.
483W / 845W |
Krell Illusion II/KSA-i400 Pre/Power Amplifiers | Hi-Fi News (hifinews.com)
This review is not that great.
Krell KSA-i400 40th-Anniversary Reference Stereo Power Amplifier | Hi-Fi Heaven (hifiheaven.net)
I would use a Benchmark LA4 preamp with the KSA i400 if I ever got it.
BTW - I should state that I have not heard the KSA i400 yet. I am afraid to hear it :)