OK - waterproof, and can take a beating.
this reminds me of marine applications -
there is no SXM Connect module for SSV Works. industry standard interface, so i'm surprised. perhaps because it is
specific to north america?
the marine application that are not SXM-Connect are cases for the add-on head-units, and special antenna, which then use the aux cable -
if you have FM in your unit, the SXM units have an FM modulator - so can bridge to the radio that way.
the aftermarket units have crappy mounting options - suction cup, or small screws, and are not shock resistant.
this is an ugly solution for a high end vehicle...although it could be stashed in the glove compartment, with a customizable foam kit.
https://smile.amazon.com/SiriusXM-SXPL1V1-Satellite-Vehicle-Streaming/dp/B00I59XQKO/ref=sr_1_2?crid=ZQAMPQBOTRQE&keywords=sirius+car+kit&qid=1554890894&s=gateway&sprefix=sirius+c,aps,144&sr=8-2
if you really want to go BT only, then add
https://smile.amazon.com/TROND-Bluetooth-Transmitter-Simultaneously-CD-Player/dp/B01B4W40VC/ref=sr_1_1?crid=19U510AYI0OBF&keywords=bt+transmitter+with+3.5+mm+jack&qid=1554891169&s=gateway&sprefix=bt+tran,aps,145&sr=8-1
weird. sounds like you have a bad aux cable, and are only getting half of the stereo input.