I have the Powerloops too on my car and there is zero drone,
Yes they are pricey, Very pricey in fact,
But they do make a nice exotic wail noise rather than a deep bassy drone,
and at idle and low revs they are very stock sounding,
Even at WOT they do not interfere with interior pleasantness
Plus they look cool too they way they loop around in the back
To the OP, Why selling them? Looking for something a little louder?