I agree that they are a little tame, but like you said, they are very hard to beat for long term listening - my ears never feel tired after listening to em.

My headphone amp is a Gilmore Dynamic V2 (since discontinued) from HeadAmp. Plenty of power, great detail and balance, 2 inputs and it can act as a preamp if I ever wanted to go the separates route with my speakers.

Here's a cool guts picture: