On the affordable end, I really enjoy my JDS Labs Atom. Its got plenty of power for planar drivers, I really enjoy it with my Sundaras. Its warmish, which I enjoy because my DAC is on the measures well but clinical side.
Dragonflys are a cool option for portable use, and could not be simpler to use in a variety of situations, but when I am using my Dragonfly Red instead of my good rig which stays at work, it seems grainy and more congested in comparison.