For my two cents, you cannot go wrong with the Prima Luna Dialogue Premiums. I have both the Pre-amp and two HPs as mono blocks. I'm a big fan. I have tried a few others, that shall remain unnamed, and none sound as good as what I am listening to now. You can spend a lot more and not get as satisfying results; if you spend less you will not get the build quality and high end components. Jus' sayin'.
Rollin
Rollin