It's been awhile since I used the W2002 with a tube amp. I really didn't like the sound of the W2002 with either the ZOTL or EAR, but I should probably try again with new source and cables. There seemed to be something screwy in the midrange I couldn't figure out. All issues seemed to resolve with a solid state amp, which is what I would have recommended until I read your post and decided to try something. I'm listening to the W2002's with the Fisher 400 receiver, and it's the first tube amp that I've seriously liked with that headphone (Melos is also good, but hybrid). Very easy and natural sound, clean midrange, bass is a bit exaggerated, vocals smooth and seductive, highs are good, lots of air. What's not to like?
I've got to try this headphone with the ZOTL again, if only to remind myself why I didn't like the pairing, and see if I still feel the same way.