I'm currently considering the Topping NX4 DSD to replace my DragonFly Red. Costs about $40 less than DFR, measures better, offers more power, has a volume knob, and does not run off of phone's battery. The drawbacks that I can see are that it's perhaps not the best build quality, customer service is nearly non-existent, it's much larger than DFR, battery life is "only" 7.5 hours (if I recall). This is all going from what I've read here, there and elsewhere. I've not actually tried the NX4 (nor any portable DAC other than DFR).
You might also consider the E1DA #9038S, which has similar form factor to DFR, measures better than the Topping, but will drain your phone faster than the DFR, and is 2.5mm balanced connection only (can't use a single-ended adapter). There's allegedly a single-ended version (#9038D) that's in the works, but apparently it requires twice as much power as the balanced (so will kill your phone twice as fast, I guess?), and there's no release date that I know of. There's also the PowerDAC V2 (PDV2), that people think is endgame audio quality, but that draws so much power that, in my opinion, it can't be considered portable. People have been using a USB y-adapter to simultaneously use an external battery with both #9038S and PDV2, but that seems like a kludge that'd be easier to have an all-in-one solution, like the NX4 DSD.
There are a number of other DACs with similar form factor and price as the DFR, but most reviews I've seen (subjectively) prefer the DFR, so I haven't done much research into them.
If you're curious about Bluetooth options, I tried the Radsone EarStudio ES100 and (based on memory and past comparisons) thought it sounded inferior to the DFR. As far as I can tell, people seem to think the ES100 is the best of the inexpensive Bluetooth DACs, so I haven't looked much into the others.
I've also been following the FiiO Q5S and BTR5 threads, and those are so riddled with complaints and problems that I mostly just read them for amusement's sake.
That said, the DFR is a very good sounding, tiny little thing. I'd consider re-purchasing it, except that my last one broke after a year and four months, just outside of warranty; plus there have been ongoing issues with the Cobalt's build quality. Those may just be a coincidence, but it does not fill me with confidence about their products. Their marketing claims are also somewhat dubious and their devices don't measure particularly well (if that matters to you; it didn't matter to me with the DFR— I thought it sounded great, anyway). Also, know that when it's connected to your phone, the DFR is not nearly so pocketable as it looks since it has wires poking out of both ends.
