But am I better off getting my cable with a 6.3mm Plug fitted instead?
Well, I decided to have the "crazy frog" cable of Gazza. And as I already had a nice cable upgrade for my portable needs, I decided to take Gazza up on his offer to fit a 6.3mm Plug and dedicate the cable for use with the iFi iCan Headphone amp. He used a Neutrik one, not goldplated, but he assured me it was "professional grade".
Well, cor blimey, there is actually a difference, it is quite clear and positive. Loosing the 3.5mm plug and adapter removed a slight edge to the sound and there is now more impact, more clarity. Als, the whole imaging is a touch improved. Sure, it is not day/night, but it's worthwhile to me.
BTW, I tried both the 3.5mm adapter from iFi and the one that came with my AT Headphones, there was nothing between the two.
So if anyone wonders, get a 6.3mm and avoid adapters is my advise..,