Excellent post and the linked article by Pass is a great read. The Crack w/Speedball and the ECP/Beezar Torpedo are the best value tube headphone amplifiers I've personally heard. I personally like my Crack better with higher impedance cans like my DT990 600ohm and modified Darth Beyers, but that's with copious tweaking and part changes. As stated, the Edcor output xformers make the Torpedo a better candidate for Grados, Denons, etc. Also don't forget about the S.E.X., output transformers and adjustable impedance switching, that's a great jack-of-all trades amp with a slightly lush sound. I love mine.
+1 - have both BH amps and love 'em both (for different cans and different reasons).