Good point @Joe Bloggs but the trade off of Bluetooth is ability to ditrch the wires....but you already know that! I definitely still LOVE RS6 wired to my IEM's, different use cases call for different solutions.In that case how about wiring your headphones directly to the DAP?
I think connecting the dongle to the USB port should yield higher quality, by avoiding an analog-digital conversion in the dongle.
Thank you for your help good sir.