Well, I’m wondering around the apartment where I’m staying doing various things this morning listening to the HD660S from my iPhone, and I have to say that I’m really enjoying them. Damn - I was going to send them back today! Maybe I’ll just have to accept that to me they’ll be a very expensive HD58X and I’ll keep and enjoy them for what they are. There’s no doubt that they do an excellent job direct from a phone.
Mike, allow me to make your life easier in this one respect. Keep them. If you send them back, you will regret it after about 24 to 48 hours. You will then end up buying them again, likely at a higher price.
If there is one thing I learned in this hobby, it's - don't sell / return when in doubt. Only get rid of what you are at least reasonably sure not to miss.