Hmm thats odd that you say the WA5 is good at driving the HE-6. I used to have that amp for a while and tried the HE-6 prototype on them and the matching was actually quite bad. It didn't have anywhere near enough power for those headphones. To me, the WA5 is actually a lot picker than I thought with headphones. It sounded completely wrong with the sony R-10 and the Thunderpants. As for LCD-2, it is a pretty good match, but way too lush sounding.
This is interesting, maybe the difference in efficiency between the prototypes and the production version was that the HE-6 was improved to make them as efficient as the K1000. I own an HE-6 and have tried the protos, but I haven't had a chance to listen to the WA5 personally. That's good to know about its pickiness, as I had generalized that it was quite versatile from reading about it in the Woo thread.
Likewise I have read a few posts from a couple of HE-6/WA5 owners that seem quite satisfied with that pairing, pretty sure they are Frank I and SillySally but not positive. I wonder how much of a difference different tubes would make with the LCD-2 for example. Have you listened to a K1000 out of the WA5's K1000 jack?
Edited by grokit - 3/3/11 at 6:54pm