Etymotic 6i?

Unless you really enjoy detailed analytical sounds, I don't think the Er-6i will sound better to you than your full size headphones. I have a pair and I at first listen, I was wowed by the detail they reveal but personally, I don't actually like the way the music sounds on them. Plus there is very little bass. On the positive side they are great isolators and great if you need to use them somewhere noisy but to get the isolation, I had to use the triple flange tips which you might find uncomfortable since they go fairly deep into your ear canal. Might help to go try your friend's pair first.

100$ is a lot for the er6i, you can usually find them for much cheaper I think.  They are very good but I would recommend the mc5's over them because they are a newer model and should have better cables and a better build.  They should also have a bit more bass.

Comparing my HF5's to my friend's er6i's, the HF5's definitely seem to be of better quality and seem more sturdy.