That said - I ultimately made the call due to comfort. I'm cursed with (presumably unusually) small ear canals - and of all the options sent with the A151 only one is comfortable for extended periods - it's not the small olive! It's the tri-flange inserted about halfway. For me this actually produces a very serviceable seal, though the housings protrude from my ears more than I'd like - it affects how well I can wrap the cord around my ears and looks funny. Would very much like to find some smaller tips. The CC51's by contrast sounded beautiful in their own right, but there was pretty much no getting around the fact that the driver (though small) actually ends up in your ear canal - and it's diameter was too big for my comfort - the smallest flanges produced a burning pain after 1 or 2 tracks.
I feel your pain (pun intended). The CC51 were too big for my ears as well. The narrow nozzle of the A151 is quite nice for small ears.