The truth is, the 650 sounds quite fine out of any decent integrated/receiver, even if not quite as fine as out of a $1000 dedicated amp. And since most people have one of those already, there's a sensible saving and an avoidance of the dreaded upgrade trap. My call is for balanced advice, not the downfall of the dedicated amp industry or its adherents.
Hmm...I guess I do deserve to be killed.
I auditioned my first pair of hp's - Quart 55Xs - on a Luxman CD player in a hi-fi shop. After that, I often listened to music plugging them into a CD player or amp. I never imagined until recently that there were dedicated amplifiers for headphones, or at least if there were, they were rare and unusual things.
Since I don't have any regular hi-fi gear to test this theory with me in Japan, I hope to take my cans into a proper hi-fi store and "listen" to some of my music using a CD player and/or amp with them. I think it will be interesting.