That's what I'm doing currently, While I don't have any other CIEMs to compare it to, I did have the Solo + SR71B setup to compare it too, and so long as you are listening to FLAC music, I feel that you will get your money's worth. But the 2 things that are lacking majorly when listening without these devices that I have noticed is Soundstage, and separation. Going back to just the straight iPhone after my previous setup has me finding the soundstage to be quite small. If this is something you can live with, I think you will get close to (rough personal estiamte) 70% of the overral experience from the Miracles by using them straight out of an iDevice.
I did find that the TWag v2 cable made a large difference to the stock standard UM cable. And think this is a worth while investment. Doesn't add any bulk, but does (in my opinion) make a noticable difference to the overal warmth and clarity of the CIEMs.
Just my 2c, if you can, trial them. If they sound good out of your iPhone 4 to your ears. Then sold!
