I'm not John, but since the CMA800 voltage output is supposedly optimized for high impedance headphones such as the HD 800, I'm not sure that the low impedance headphones would excel in this setup. I've used TH900 at 25Ω with the CMA800 to good effect, but I don't think that those headphones are a good basis for comparison, since they have their own sound signature by far and away, altho they may be close enough via the Denon sound for a valid comparison with the LA7000. I'm sure that John has audited a much larger scope of HPs vs. amps, anyway, so his response should be much more cogent.
My current CMA800 match fave is the LCD-2.2 at 65Ω. They've never sounded so good, but that may be more about power than impedance matching. I've got a pair of T5p at 35Ω around, but somehow they've not managed to come out of their case of late, since I'm having so much success with the forementioned 3 headphones above with my current amp setups. And concerning rattesp's T1 comments, I'm not sure if if they're ever gonna.
Edited by jacal01 - 1/6/14 at 1:24pm