iPhone drives them without problem, but the treble is more recessed compared to O2/ODAC driven. Isolation is quite good, better than my aJays IEM.
They leak a little when played really loud, otherwise they are quiet on the outside.
I love K550 as well but like you said, I would not wear this out as well. I've once been asked on why I am having two mushroom on my head ..
Is the VK-1 difficult to drive? I would be driving this straight from the iPhone, would be good if I don't need to take the HP-P1. Also, how's the clamping force and noise isolation?