I did compare my own L3000, an edition 8 & the HD800 on a Lehmann Audio Black Cube and Naim CDP. I liked the HD800/Lehmann combo, but the L3000 and Ultrasone (both closed) have more bass. The Ultrasone on a SPL Phonitor amp to much so for my liking. Can't say how the Lehmann compares to the Donald North amp. (Still like the L3000 best, but have ordered the HD800.)
From what I heard I would rank amps for the HD800 like this:
1) Lehmann Audio Black Cube
2/3) Naim and AT-HA5000
4) SPL Phonitor
Funny enough that's reverse to their cost... I only noticed after the listening sessions and ranking since there were no price tags.