I doubt you will need an attenuator or padding of any kind, though it certainly is an option. I've used powerful amps with 104db LaScalas and had no such problems as you're anticipating. My friend was running a 200wpc Mac amp with Khorns which have a 104db efficiency rating - Don't recall any problems there. I'm currently running 500wpc mono amps into 92db efficiency speakers with no problems at all. I don't get much past 9 O'clock on my volume, but that is really not a problem (it still is a smooth transition, over a shorter rotation). The combination I'm using sounds wonderful to me (not necessarily because of the pairing of high power and efficiency). Obviously your speakers are likely a great candidate for lower power SET amps, as Tarsando points out. That's not to say they can't sound great with another option. Certainly with the higher power amp you will not have to use nearly as much of the volume, but it is not going to be an all or nothing scenario.
Marco
Marco