Chain of command

Greetings,
     I have an ongoing lack of understanding about what piece of equipment in the following system, actually gives the music it's final quality out to my speakers.
  
**Thumb-drive with 48000Hz, 24-bit .wav music---to Samsung Android phone---analogue out of phone's earphone jack---to input on amp---to 16 ohm speakers.**

      Will a quality amp, tube or other, influence the quality, or is it already set by the phone's DAC?
      I only want to use the phone for it's interface to select my files to play.  I have read that any DAC connected to the phone's analogue earphone jack, ...will by-pass the phone's DAC?  This comment has been both substantiated and ridiculed, so I'm at a loss here.
      Seems to me that the earliest the quality is set, that anything after will just be upsampling.  
Is my most logical route to buy a DAC with a visual screen for file selection?

Any help here....would.....ah, ....help!
Thanks.