I use my iPhone in my armband with speaker end up. bump the volume up a bit and it works fine (well it's not stereo but come on it's tunes and you are riding...).

I hear the traffic and the tunes just fine. no problem. Oh and I have also played ipod while the iPhone is in the iPhone bracket on the handlebars and again it's fine. I am hard of hearing (deaf in left ear, not so good on right side either) so I am guessing what is loud for me would be a lot louder for the rest of you hearing unchallenged. YMMV

look ma no earbuds.