New Krell s550i Impressions?

Not all Krell amps need 20A power line. You should check manual

I had one for about an hour and the power supply went, Bought a Mac6700 instead MADE in USA not China

I am considering one of these, but would be using it to run a pair of 4-ohm KEF three-2's. Anyone have an opinion as to whether this would be too much power for these speakers? I don't play music at concert levels, but my system is in a very large room.

It is not for the power, it is for the quality...

There is no such thing as too much power .
It is a known fact that dynamic transients in music can exceed 10 x
The rated power in milliseconds. This s why by having the extra power the extra headroom is a Big plus.
The amplifier is coasting and not having to go into distortions. I run Maggi
3.6, as well as big Revel speakers with the 550 with no problems whatsoever. in a
16x22ft room .the volume on this is a very high precision ladder type
That goes up to 150 for a lot of flexibility.