Good evening,
I'm not going to try to compare the DX170 to the Cayin N3 Ultra or the Hiby RS2, they are all three different. They are certainly in a similar price range but their characteristics are very different. And if you mention his models it is because they interest you. The only advice I can give you is to do like me. find out, including on this forum, about the DAPs that interest you, read them all, go to the manufacturers' sites, your local resellers, look at the reviews, prices, after-sales service (hardware and firmware) if you can test them. Define your use of the DAP, the headphones you will use, the type of music you like. None of the 3 DAPs “sounds” the same. So see which one suits you best.
Caution If, for example, you like music that "hits" loudly and your headphones also "mark" the bass, if you also take a DAP that "pushes" the bass a little too much, this risks creating a lot of bass and distorting the bass too much. that you listen to.
Personally I prefer headphones and DAPs which are as balanced as possible so I don't "mark" the sound too much and if I want for example more bass I can use the equalizer and control the balance of the sound.
NB: I don't know when the DX180 will be released but if I had to buy a DAP (unless your need is urgent) I would wait for it to come out because it will be superior to the DX170 and could make the comparison with other DAPs obsolete...