Explain fussy. Out of all the amps I've owned the below three are the ones I didn't like the HD800s on at all. However, the fact was - I didn't really like any other headphone on them either.
Burson HA - 160D
Of course they sound better on some amps compared to others - all headphones do. I'll bet there's someone out there that loves their HD800 on both the 160D and the Magni.