I've had the dx260 for a couple of days now, here are some initial thoughts in random order.
I've been trying to compare it to the dx240 (AMP8 MK2S) and to my ears the two are very similar. I think I detect a bit more mid-bass in the dx260, but if so, it's a very subtle difference. It's really hard to say if the 260 sounds better than the 240, but time may tell on this. I even tried comparing the two iBasso DAPs to my Shanling M6 Ultra, the Shanling seems a bit darker, but once again the difference seems subtle, if not just in my head because I want to like the 260 better. In a blind test between the 3, I don't think I would be able to tell them apart at the moment.
As far as power goes, I listen with my Solitaire T headphones and there is much more power with the 260 vs 240. On the 260 I can listen on low gain with the volume around 40, whereas on the 240 on medium gain the volume is around 60. That said, I never had any problems powering with the 240, but just that there is a difference.
Using Roon Remote and Roon Arc, the 260 is faster and more responsive than the 240, I'm guessing because of the faster processor.
The 260 is slightly wider than the 240 and slightly shorter, and apparently is lighter, even though my hands tell me that the 240 is the lighter one. I think I prefer the size of the 240 as it just fits well in my hand, but this is not a deal breaker. Also, the volume wheel on the 260 feels flimsy and cheap compared to the 240, again not a deal breaker though. Other than that, like the 240, the build is excellent.
I'll keep listening to see if I notice any other differences and post back if anything changes.