Someone get them to redesign them!
I don't know how strong the headphone out on the iPhone is, so I can't compare. I never found my mp3 player to be too weak, but there's definitely room for improvement. I'm just not looking to carry the bulk of an amp for my current on the go buds.
If Etymotic ever decides to come out with a sleeker ER4S, I'd be more than willing to carry an amp then. I only needed to hear one song before I knew it's sound was for me. I've yet to hear another IEM anywhere close to what I like, so I was pleasantly surprised when I heard these.
I used to own E500's and with a bit of EQ, they sounded decent, but some songs would just be downright odd sounding. That plus I used to drive to work and be able to listen during work was part of the reason I kept them for as long as I did, but I eventually sold them because I rather not keep a pair of $300 IEM's that I need to tweak to enjoy ~75% of the time. That and I got some Yuin Pk1's from the NY meet around the same time and they sounded great without any EQ. But now I switched jobs and public transportation in NYC is just too loud for me to listen to the Pk1's at a comfortable volume. I either can't hear music or I turn it up, but end up with ear fatigue.
What I've always wondered was what's the next closest IEM that sounds like ER4's? I used to ask what's the closest sounding IEM to K701's, and I think ER4's were as close as I can get (very very very gross generalization about treble and bass only. I didn't have time to listen for anything else). Any ideas?