I am using the case for AMP+ I bought in your shop. Distance between devices is only 2-3m. Yes, I am using the power supply for the AMP+. This should be sufficient as to the statement in m2p webshop
All of our offered hardware is tested extensively and is optimally compatible with the Max2Play image. No Linux knowledge is necessary for our out of the box solutions.
Ok, that is advertisement. I will try a seperat power supply for the Pi3 and an external dongle for bluetooth.