Many users believe they need a custom ROM or special app to get EQ goodness in Android. Google has baked in this EQ goodness in Android and using it is very easy. Open the default Google Music app, then load and play any song.
Click the Menu button (three little dots) and chose Equalizer
Once here, make sure you toggle the switch to on.
Choose the style of equalization.
These settings aren't device wide (aka they are only for the music app) but they can provide a nice punch when needed.