So I've decided to get the Pono and am looking to upgrade my open headphones from Grado sr80s to what I've narrowed down to a choice between Hd 650s and Fidelio X2s. I was hoping some of you might be able to weigh in on their sound on the Pono (I've read about 650s and Pono but not X2s and Pono). I was leaning heavily towards the X2s but the possibility of playing the 650s in balanced mode has me rethinking... The 650's are about 50 euros more, plus the cost of balanced cables, and their high impedance makes me a bit nervous. The X2s are low impedance but can't be easily modded for balanced use as far as I know.
Thanks for any input as to this choice relative to the pono.