I finally got the hear the DX160 today, and compare it to the Hiby R6 Pro.
I checked the Wifi / BT was connected, and listed with player paused, and whilst playing music, and couldn't hear anything untoward on the DX 160.
I also discovered that if you headphones have a mic on them (like on my B&W P7W), that the sound is intentionally crap, so as to discourage you from using them, as it would be perverting the pure audio coming out of the unit.
So, agreeing with the sales guy, that this probably wasn't the unit for me, ... I asked him if he'd had any returns here in Singapore.
Firstly, they've sold waaaaay more of these that the R6 Pro, and only had one defective unit so far, ... but nothing to do with hiss / interference etc.
I was pretty impressed with the sound out of it -- honestly I couldn't tell the difference between that and the R6 Pro!
There was quite a big difference in weight tough, as the R6 Pro was the stainless steel version! It was like holding a tank in my left hand, and an iPhone in the other. Super solid, .. but probably too heavy to be lugging around in your pocked all day.
Anyway, ... so from my small test - sound quality was great - and no noise / hiss to be heard.