I also use an OTL amp on my HD-650 (LD MKIVse) and love it. But to be honest, when the HP is connected to the OTL and sounded super mega good, I get distracted listening after some time because of the anticipation and urge to switch back to the Lyr. Then when I am using the Lyr, I have the same feeling to switched back to OTL!
It is tough! I have Phillips JAN ECG 6922 (the blue labeled ones) in the Lyr, and Russian 6H30/ CBS Hytron 6AK5 in the OTL amp.
I just acquired an output transformers from Sowther with HP taps to use in my 45 amp to see how it sounds with HP's. When they arrive, all hell will brake loose for sure! :>)
Oh the suffering trials of audiophilia.....