Well... I've figured out an alternative.
1. Make sure to switch your output from Amp to Line; huge diff in the output... duh.
2. I abandoned the headphones and plugged the left and right outs of the X3L into my keyboard amp.
A little tweaking with the Tone Volume and I was in business. It's loud enough to feel it, but not too loud to annoy the neighbors. Head and shoulders above headphone. Wish I could find my Bose headphones just to see if it was ear buds... tried by Shure 425s and not much better.
es336td's post in X3Live MP3 In and Headphone output problem was marked as the answer