The Lyr was my amp before the Mjolnir. It was still in the stable when I owned the Gungnir so I have lived with the system you are now putting together. I'd recommend rolling some Amperex Bugle Boys (60's Herleen factory O-getters) to dial in some surprising synergy with the HD800. Enjoy.
By chance, I have rolled exactly those tubes into the Lyr, giving the Telefunken E88CCs a rest. I'll leave them there until the Gungnir comes - thanks for the tip!