“I've tried many unofficial 2-2.5 Amp chinese power supply, many of them couldn't supply enough power for the pi3 at 100% CPU use (without any periferials).
This one works like a charm, there is no power shortage. Recommended!”
“I used a 2a quickcharge adapter before, but my pi had some issues running at full speed with my retro pi installation. The 2.5a official power supply fixed that issue for me!”