As others have pointed out you don’t need a lot of power but you do want clean power. The design of the speaker is such that many solid state amps will sound brighter and harsher than normal (this is part of why horns got a bad name; nothing to do with horns in general so much as its just a poor match) due to the impedance curve and the design of the crossover.
Also as others have pointed out its that first watt where you are likely to do the most listening, so you really want to make that watt a good one. But the power after that should be clean too (this is where SETs fall apart) because with any good system, even though it might *be* loud, you don’t want it to **sound** loud. If anything, that single quality is what sets a great system apart from the rest. So the amplifier power should remain clean as you run up the volume.
There’s a funny thing about how we hear and amplifier power in general. For each 3dB increase in power, which is doubling the amplifier power, the increase in volume isn’t that much. A 10dB increase in power is perceived as ’twice as loud’ and that requires a **10-fold** increase in amplifier power. The result is that when you run up the volume you can wind up using a bit of amplifier power (even on an efficient loudspeaker), and in practical terms this means that SETs will not be able to show the system off, since you really don’t want to run them past about 20-25% of full power, otherwise distortion will cause them to sound loud. I know this seems tricky, but the ear has several rules that are the same with everyone- it interprets distortion as tonality, and it uses the higher ordered harmonics to sense sound pressure. In SETs above that 20-25% power level, distortion in the form of higher ordered harmonics shows up (initially on transients) and so causes the system to sound loud- not because it is, but because of the way the distortion interacts with the ear.
Which Klipschorn do you have? Is it the corner horn version? How big is your room? This will say a lot about how much amplifier power you need.
