some background:
came from
Galaxy Note 3
Fiio E18
Sennheiser IE80 with Galaxy Audio silver cable
Beyerdynamic Custom One Pro with Dynamique Audio Silver Cable
I didn't think this setup could get any better, and it would be just the law of diminishing returns.
As of now, I couldn't stand the lag that was building up with the Note 3 so I swapped that out for the iPhone 6 plus,
and after many many many months of debating, the Shure 846s.
I don't really see the need for the E18 with the iPhone 6 plus anymore as the output seems to be quite good without amping,
Even the COPs sound fine without the amp. Also, the micro USB digital out cable no longer works with the E18 on the iPhone and the 3.5 mm to 3.5mm seems to be reducing audio quality as well, so I just use it for my Surface Pro 3.
The only issue I have with these is the fitment. The rear round part touches my ears so it hurts after a while. I had similar issues with the IE80s, but after getting use to them the pain went away, I guess my ears need some breaking in
Other than that, I'm listening to movie OSTs in FLAC like The Lord of the Rings, Harry Potter, Pirates of the Caribbean, The Hobbit, hell even Kung Fu Panda and I'm loving the soundstage and clarity.