I LOVE the XC / HA-1 pairing. You can read my impressions here.
My post is a little enthusiastic, but I still feel the same.
Edit: I'll add to my impressions that nothing I own sounds as good as my XC, but my XC sounds better on the HA-1 than anything I've tried them with. The HA-1 easily reveals the limits of my other headphones if they can't keep up to the unit.
Edited by x RELIC x - 6/12/14 at 8:06pm