I think you should try the manufacturer of the Speaker. :)

I think the point is being missed.  While the devices do need drivers of sorts, the bluetooth on the PC side also seems to need A2DP drivers that support the class of service the stereo headphones are able to also support.  That is possibly the cuplrit here.

Try updating to the Dell Wireless 375 Bluetooth Driver v6.3.0.7900-A05 R296919 and see if that helps.  You might need to uninstall the WIDCOMM Bluetooth drivers first, reboot and then install the new ones.

This worked to fix a few E-series models that used the 375 Bluetooth module.