How did you establish channel levels for each speaker to begin with? Why did you set the gain knob at that particular position? You turned each channel level down from a default value of 0 to -7 in your pre-pro? All the speakers are set the same? You have the same speakers at the same distance from your listening position all around you? You might want to describe more what you're doing with REW to set levels....
I wouldn't make that assumption about the attenuation knob detents on those amps let alone think about it that way. The attenuation knob is there simply to adjust gain for your pre-amp's output level. I generally set my Crown amps to where it will just start to clip at the very highest level I'll use it at. Percentages and dB don't mix well together in any case as dB is a logarithmic scale.
Those BIC are relatively sensitive speakers and they're likely not using the power you think they are; they will likely sound bad and have you reaching for the volume knob before you reach their limits. Use an
spl calculator like this to see the relationship of distance and the sensitivity of the speaker for power needed. I don't know how BIC rates the sensitivity but I suspect it is overstated at 98 dB, I'd probably use 4-5 dB less in the calculator at a guess (like I would do with Klipsch). I can't find any measurements from a 3rd party for these speakers, though. Speaker wattage ratings are perhaps useful as far as a limit goes, but not generally a very useful spec in general. Changing from a 200wpc amp to a 300wpc you would only gain 1.8 dB.....
If worried about feeding your speakers too much power, that's usually easily accomplished simply by using reasonable care with the master volume level. Drunken parties could well be different, though
(and setting a volume limit on your pre-pro, if yours has that feature, isn't a bad idea, even just for own general use).
