I've just found an app which, in my opinion, greatly increases the sound quality coming through my DBA-02's.
It's called EQu, and it's basicly a fully fledged EQ monitor. I can change the EQ on the fly, and after finding the right setup for me it felt like I was using completely different IEM's!
The main screen of the app
The EQ line, changeable on the fly. Or you can use one of the presets.
The (bland) music selection screen. (Don't laugh at my taste :P)
it's not without its flaws though. You can't scratch tracks and the music selection screen is very basic.
You can only pick playlists or the entire music library. No album or artist view.
Also, I've noticed that sometimes when loading text or a webpage, the music would become distorted. However only for a very short period of time. Lastly, if you do not lock the screen you could accidently change the EQ by brushing your hand against the screen, there needs to be some sort of lock for the EQ while you are playing with the options etc.
Other than those issues, this app is brilliant. I've not used a portable amp before with any player, but now I don't feel as if I need one. This app is a must-have on any ipod touch/iphone I'll have the pleasure to own, now or in the future.