I have found that the C7s sound better with more power. Some say they are dull speakers, but when they are provided with sufficient power they can sound dynamic and agile. I'd suggest 100 wpc as a good minimum. So, something like the Cronus Magnum 2 or the Primaluna Dialog Premium HP (w/KT 150s) would be sufficient power from a tube amp. Harbeths sound quite good with solid state power as well, and there are many solid state integrated amps at 100 wpc and above. A tube preamp and a powerful SS amp would also be a great match with the Harbeths.
Good luck! Scott
Good luck! Scott