Tubes likes higher ohm headphones better then low ohm headphones, its a natural match between the two. solid state (even the kind in your ipod headphone out) like low ohm's better. this is why people say Grados sound better then Senn's going strait from the headphone out on portables.
Grados don't like tube amps and tube amps don't like Grados, even on my hd-25 (which is a Grado lover) the Grados will just not have that natural match as they would with a Solid state. they may sound really good but not as natural. Your Beyers being 600ohms would make love to the Raptor all night long and the Raptor will love the the Beyers cause of the high ohm match tubes have.
I just notice the 600ohm Beyers seem to have really come into there own!
Everytime I turn around the Beyers seem be be on top of the Raptor or visa vera! I think they like each other!
You cant get the "gang" to buy into the Raptor Billy? Come-on your the friggin President!