Yeah, I am using an iPhone 6s Plus. I am at about 70-80% volume and I could go to 100% without hurting my ears. I don't have the standard cable with me to compare but I recall it being quite similar.
EL8s are great and I highly recommend them, I just don't think the cipher cable is anything to hype about. I mean the DAC may or may not offer anything (I think DACs vary very very little from the ones in phones to desktop monsters, they convert 0s and 1s to wavforms, it's a simple process and they SHOULD all do it the same, anything else is coloration).
As far as amping goes, well it gets its power from the phone itself as opposed to an internal battery or external source, so, how much more juice could it give them?
I like my Titaniums and use them every day at work, but I got them because I didn't like the aesthetics of the standard wood veneer EL8s (which I had bought first and returned), and that's the only measurable difference I can find.