crack, WA3, Asgard 2, those are just a few off the top of my head that would do great with hd 800.
umm they're not hard to drive, but they're hard to get a good setup for. they can sound analytical, bright, bass light, or bland with the wrong setup. ive noticed u really do need a transparent source and a great amp to get them to really shine.
they're starting to even outperform my Beyer T1 with the right setup, the Hd 800 really are my best headphones.