Yeah, like I said with 250ohm DT880 I felt NX1 was driving them fairly adequately on high gain. More than substantial.
I don't know about other owners but I really enjoy my NX1. It's proving to be a great little investment (and sooo cheap)
I want to monitor the power though after many hours have been put on to see if there's a drop in performance say after 30-50 hours.
After around 50 hours I didn't notice any drop in current.
I was changing cables around the other night and felt like it was straining at one stage. I was unsure so I topped mine up.
I've found using the stock cable that comes with the amp pretty decent and tidy.
Btw: If you're already near a full charge (say 2 weeks) the NX1 will top up in about 30-40 minutes.
Like with BH I'll tend to charge mine before it goes flat rather than let it drain. Probably about 1/2 way.
It's good practice with Lithium batteries not to let them drain completely. Actually it is better for longevity to charge the battery more often then not.