I'm running them with an 80 watt receiver. They get plenty loud enough.
For imaging (location of the instruments) though, you have to give them some space. I have them just over 4 feet apart and I have to be back over 8 feet to get a convincing soundstage - a wall of sound so to speak. Unless the recording is very good, I can close my eyes and pinpoint the speakers (i.e. the ribbons) from the very high frequencies.