Not sure if this is an option... Do your buds have their own volume control? If so, maybe you could try putting the M9 in "LO" or Line Out mode (which sets the output volume to MAX, so be very careful) and then control the volume with your buds? My Beats wireless have their own volume control. Maybe this will work for you.
I use it in LO mode in my truck because the volume is a little low for me as well.
Seriously though... test for volume level BEFORE you put them in your ears... there is a warning message on the M9 screen reminding you when you change to LO mode.
To do it, swipe down from the top of the screen, and click the little headphone icon... it will switch from there. You can change back the same way.
It may be that LO only works for the output jack and not with BT... just thought you could try it.
Holler back if this works for you.
Peace