Just equalizer settings. I don't believe there was any special hardware in those phones. In fact other phones actually have better d/a converters than the HTC.
I would say just download any equalizer app, and boost the bass and treble. That's pretty much what the beats software did.
The sound quality you hear will still be dependent on the quality of the file. i.e. lossless (wav, Apple lossless) or crappy mp3(includi pandora). Also good headphones (beats are OK, but struggle with detail) will help.
Sent from my SAMSUNG-SGH-I727 using AC Forums mobile app