Scott,
I compared the 10's and the 15's side by side at the store. We had the CD player going, then set the tone on both the 10's and the 15's to be about the same. After that, I just plug/unplug the audio cable between the two pairs. The 15s clearly stood out with both volume and bass. So far, I hadn't got a chance to use the full volume yet - I guess the 15s were more than what I need?

..rb