The point of my post was that IMO, it would be a good idea to keep the power of the external amp sort of close to that of the internal (bass) amp, which is 200W.
. . .
you will find that you are raising or lowering those bass controls to match the woofer output to the panels when using a more or less powerful external amp.
Neil,
I haven't really found this to be the case with the Sanders Sound Monoblocs (1600 watts into 4 ohms). As much as I can turn it up, the bass seems to keep up with the panels beautifully. Granted, I have no idea how much actual wattage I am using of the amps capabilities and I have done no test tones at really high volumes to see if there is a limit to the ability of the woofers to keep up. But I would say in practical terms, this is a non-issue.
If it were an issue, wouldn't you really need to not exceed 400 watts to the panel, since each channel has two 200 watt woofer amps, for a total of 400 watts going to woofer output per channel?
Also, isn't it really more important to match the voltage gain specs of the woofer amp than the total wattage? I don't know how you would do this since they don't publish this spec that I am aware of. Also, it seems their electronics module takes this into account in compensating for the incoming signal. I guess it is once you have exceeded the maximum voltage gain of the woofer amp at the maximum wattage of those amps that the wattage of the panel amp would theoretically start to play a factor. Again, I think for all practical purposes, this is just a non-issue.
Finally, you reference using the 25 and 50 hz. level controls as some sort of woofer volume attenuator used to match the woofer response to the panels, but that seems very misleading. These controls attenuate the volume at subwoofer levels, but they don't really attenuate the entire woofer response (up to 250 hz.) and aren't designed to be used to match woofer response with the panels (isn't that what the crossover does?). These are really subwoofer equalization controls designed to finely tune the subwoofer response of these speakers to the room. If your room excites a particular mode under 100 hz. these controls can be used to attenuate the effect of that mode.
If the room is properly acoustically treated, these controls should not have to be manipulated as the preamp volume level changes. Volume level does not change the modal response of the room, does it? I can think of no reason to manipulate these controls depending on the power of the amp, as you suggest. If that was really necessary, wouldn't ML have just included a woofer level attenuator, like they do on their subwoofers? I think that is part of what you pay for with these speakers -- a fancy electronics module that, among other things, matches the woofer response to the panel response (pretty much no matter what amp you use to drive them).