So I've just got myself a FiiO X3, I'd try to plug it to my Q701 and see how the pairing perform when I get back to my home country, where my Q701 setup is. The X3 has got enough power to drive the HD800 to an ear-damaging volume, though it doesn't sound good at all. But I have a hunch that the X3 would be a good match for the Q701.
FuzzieKiwi,
I noticed in your sig that the Magni is in your wishlist, if you are planning to use it to drive the Q701, may I suggest you to rethink that plan? It's not a bad pairing, but at times can be a bit sibilant. The Vali might be a better choice (I've never heard it though). Those who have heard the pairing may be able to give a better insight.