I'll tell you why I liked the A2. The main complaints heard about the HD700 is: a) some harsh highs b) lacking bass. I tend to agree with that...with the wrong equipment. When I first got the HD700s I picked them up at the post office on my way to work, so I only had my X3, and E12 in my car. I tried the HD700s on both of them and thought they sounded awful: highs were extremely harsh, and the bass and overall sound was just very thin. When I got to my office, I plugged them into my E9, and they sounded a little better, but I was still feeling big time let down by the 700s.
I go home and try them on the Oppo 105's direct headphone jack, and they sounded good, but not worth their price. Now keep in mind, I've used the HD650s on all these devices and they have always sounded fine. In fact, I had used the HD650+E9+"whatever source I preferred" combo for over 2 years, with really no complaints, and completely loving it. The HD700s just did not sound great on any of these devices. FInally, I saved the best for last and I plug them into the A2. Now things were beginning to get better: the highs were starting to get tamed, and the the overall sound was starting to fill out, after a few more weeks of break in and use with the A2, the headphones were really starting to shine. When I added the UberBifrost to the mix, it was over: the cans were truly spectacular.
I don't know how how the HD700s perform with the Lyr+Uberfrost, they might well be better, but I do know that for me the HD700s didn't start to shine until they got to the A2. I have no first hand experiance with the Lyr, but from what I've read on Head-Fi, the A2 is actually the 'warmest' of the 3 mid-level Schiit amps, and that is exactly what (I think) the HD700s need: a warm amp to tame the highs and fill in the sound and give the bass a little more thump. Of course, the idea that the A2 is warmer than the Lyr is purely hearsay for me, and you would know better than me about that since you've had first hand experience with both amps and the HD700