I agree with Anak. The DX100 is incredible for what it is. The firmware and overall slowness and irresponsiveness to other playback software is troubling, BUT there is next to NO noise from the output, it handles a large range of headphones perfectly, and plays all important files out of the box. My purchased AAC work fine and so do my CD-ALAC files as well as FLAC, MP3, and others. I'm very very impressed. I'll finish a full review at TMA soon and conclude that this is the first Android device I feel is worthwhile - and that as an iOS forever user.
Problems with firmware MUST be fixed - there is no excuse for the sloth, but next to, say a C4, and HiSound, it handles ID3 much much much much much much better, almost enough to make one toss one's salad when returning to the other manufacturer's POS players. Soundwise, the C4 and DX100 are neck and neck, though the DX100 is better for sensitive earphones (less noise, no clicks and pops), but the C4 is much easier and faster to use.
No problems with power for either. I feel that the DX100 is the best device for people who are coming from the perfect running iPods and iPhones and who want a more powerful player or want to jump into the audiophile world - that is, when firmware is fixed. Currently, no dice. But, I'm looking forward to when firmware is fixed. No questions asked.