Lyr or LD MKIII - either one will drive the HD650 acceptably. Myself, I'm just not a fan of tube amps. I haven't listened to a lot of them, but it seems that I'm only happy when I hear the > $1000 systems. For that kind of cash, I'll stick with a nice neutral solid state amp. The warmer sound of tube amps just doesn't appeal to me, but again, that's my personal opinion based on my ears and brain. In no way should it influence what you decide to try to improve your listening station - to each their own!
does the lyr or ldmkiii drive your dt770 250s any better than they do the hd650?