Considering it is a high end electrostatic rig I think it is quiet portable but to me KSE1500 paired with anything is in the realm of transportable. Portable is something that you can put in ones pocket and require nothing else but that.
That is my definition of portable.
A bit of update with AK70 pairing with various IEM, I really do enjoy the pairing with ATH IM04 and IE800.
Every time I listen to the IE800 I am amazed on how wide it is. I wish it just had a better fit and there was a cheap way I could try it on balance format.