On the subject of amping, there is no blanket answer as to whether these "need" an external amp.
If your source player (phone or dedicated audio player) has a good quality DAC/amp, then external components are not needed.
If your source player has lower quality components, then higher quality external components will help.
While researching for my latest phone purchase I specifically looked for one with higher quality audio player components. I ended up with the HTC 10 which sounds great with the P1.