so I don't really add my $0.02 all that often, besides most of the old timers here are much smarter than I ... but to answer the question, I haven't worn earplugs with the headset in.
I have the GPS/Phone volume from the GPS unit set to 100%. I have the music set to 60%. At over 55, I cannot really make out the music so I tend not to use that function too often. I don't have a problem hearing phone conversations at any speed. I do feel that the helmet plays a huge role with the audio quality. My HJC (even though I don't like the helmet) is much more quiet at speed when compared to the Scorpion.
Hope the little Ninja is treating you well. I'm happy with the BMW, but it costs tons more when you do stupid things like hitting potholes thus requiring a new wheel.
... but to answer the question, I haven't worn earplugs with the headset in.
