The Topping NX4 DSD is one of my favourites when it comes to portable DAC+amps. It's small and portable, it is well built and it has enough power to drive most headphones. You can read my review, if you wish, for further thoughts and analysis: https://www.soundphilereview.com/reviews/topping-nx4-dsd-review-1798/
Slater91I appreciate this review, it answered a lot of questions I had. I was also looking at the iFi Nano iDSD Black which you also happened to review. I'm looking for a mobile Amp because I like to take my Senn 6XX (these are the only difficult to drive headphones I have) onto the back porch sometimes and I feel pretty silly hauling my LCX desktop amp and extension cords back and forth. I'm glad you mentioned possible problems with sensitive IEMs but I don't plan on using this device for those, my FiiO x1 treats them well enough on it's own. I'll pick the NX4 over the iFi device since it's a bit cheaper and seem very comparable.
There's a NX3s drop going right now for $55 and I'm trying to decide if it's worth it to pony up for an NX4 at $150. Do you have any insights for me?