How can I tell where the best sound quality is?

Not quite sure what you want to know but this might help

Bitrates and MP3 Conversion (http://www.mp3-converter.com/bitrates.htm)

I have a really cheap Coby MP3 and I am really happy with it. I noticed the speakers or the headphone I attach make the difference more than the player itself. I use $30. Sony headphones mostly.