I am interested in the same thing. I just installed a Parrot ck3000evo with a CTPPAR007 module from connects2 and everything is ok other than the volume. I cannot use it because of this. While driving it's too low to have a conversation.
I've read that some people added another speaker for the ELK-800 but I don't know if that the proper way. I sent an email to connects2. Is you BT the OEM version or an aftermarket one? Can anyone give us some tips please. I have a 2000 X5 with DSP, no NAV.