Can't say I tested many, so I probably should say from what I read. Planars are a no, no for sure and I've heard Senn 650s are also not a good match. One day I will try plugging in my LCDs and see.
If you search what Vinnie Rossi of RWA, says about AK and full size cans it is the same thing as I did. He is an expert and very well thought of in the Audio world.
The AK is a stellar product for IEMs.
I have tried my A&K120 with my HE-500 and like the combo a lot, certainly it sounds better with a higher powered output/amp but the sound was quite good A&K1200>HE500