I don't think it is a power issue for the AQ for it does work ok..but not blasting as I've heard from a few post on the D2...., but it maybe for the Excalibur.. the excals audio output is only .33mW's...
Now I have see a few say the audio on the D2 with the bonephones was just ok.. I see so many different reports who knows. One guy, Paystreak said the D2 with bone phones will rattle your head. Then another hunter on Steve's forum said he had to put them to his ears to hear them best. Now that is the way they are with the excalibur.. So who knows.
I'm going to ride the summer out with what I have, with gas going up and everything else, I will be hunting less this year so maybe no need for a new machine.