I brought the HD650's home tonight to A/B against the LCD3 on the Woo Audio and SR71a amps.
The Woo heavily favored the LCD3, no two ways about it. They had more body, better tone, and cleaner resolution than the Sennheisers. At first listen, the HDs were very enjoyable, but a switch to the LCD3 showed an immediate and noticeable improvement. Was it a 5-6x improvement (the cost difference in what I paid for each headphone)? No, but I always preferred the LCD3 on the Woo. Really nice pairing.
Switching to the SR71a, similar differences, but the HD650's seem to shine on the Ray Samuels portable amp in a way they didn't with the Woo. More dynamic, more presence, and just more musical. I noticed the difference much less on the SR71a, and right now, have been quite happily listening to this combo without feeling slightly cheated as I did listening on the Woo.
My respect for the SR71a has really increased. For a portable amp, it really offers so much of the musicality of tubes and nice class A desktop amps (the Burson conductor comes to mind). Never bright, never dry, just really sweet and always musical, with every headphone, but a real nice pairing with the HD650.
So...glad I invested a little bit in the work system, and happy about pairings and choices in the home system.
I used Shawn Colvin (Something about Jimmy), Bob Dylan (House of the Rising Sun, Oxford Town), Sheryl Crow (misc), Alan Toussaint, and always some JJ Cale, Harry Nilsson, and John Hiatt (Crossing Muddy Waters) for the comparisons, if that helps.