Actually I sold the Woo Audio 6SE. I find it more that powerful enough for my Audio Technica W11R which is low impedance. Great all in one package for low impedance headphones at least. The WA 6SE didn't offer much more honestly. Just tube rolling options. I had the Beyerdynamic T1 but stupid me forgot to try it out of the Anedio =/ Maybe someone else will be able to chip in more impressions of high impedance headphones through it.
Also, I sold almost all my dynamic gear except for my ATH W11R and my Anedio. I'm going the Stax route with a Stax Omega 2 MK1 after having heard it at a meet.
Thanks for the comments. It is interesting to hear you say that a respected $1k amp doesn't offer much improvement over the built in amp. That mirrors my findings as well. Unless you really need the power for a planar type headphone, or a high impedance headphone, the built in amp is a very compelling option.
You should really enjoy that Stax setup. I do miss my O2 MKII, and even my 4070 at times (although those were about as flawed as they were brilliant so I couldn't justify keeping them). I might revisit some Stax one of these days.