I keep my A2 tucked under a computer monitor, so I can access the face of it from under the front of the monitor (next to the monitor pedestal). Surprisingly, barely a trace of the considerable heat generated by the A2 can be felt on the bottom or back of the monitor, even though the monitor bottom is only about half an inch above the A2 faceplate. The A2's top vent is mainly behind the back of the monitor, though, with air to breathe. Point is, the A2 is as hot to the touch as everyone says it is, and deserves Schiit's cautionary commentary about it, but all that said, it actually dissipates the heat quite effectively.
By the way, after only a brief confirmation-of-operation listening session with my HD-650s, the A2 was obviously superior to the integrated headphone amp in my Meridian Explorer (v2 with reduced output impedance). Not that that'll surprise anyone, or that the ME amp section is poor, but I found the confirmation somewhat gratifying. So far I'm very happy with the A2, fed by the ME, driving Airmotiv 4s, with a mix of file types and genres from lossy to 192 kHz. I'll get some quality time with the HD-650s at some point, but transfixed with the speakers for now.
One other minor observation so far is that the sound is so "clean" that I don't realize how loud I have the music until I get a little fatigued and turn it down. That's the point I realize, whoa, that was pretty loud. Kind of like boiling a frog on the way up. Point here is, distortion or sibilance or some other harshness is not the factor limiting listening volume for any length of time.