Time for an update. Just the ones I have here now (i.e., not my Sextett or HOK80-2, which are in storage in Berlin).
1. (tie) Stax SR-Lambda
1. (tie) Peerless MB PMB500 floats
3. (tie) Yamaha YH-100 (Wualta-modded)
3. (tie) Stax SR-X mkIII
5. Realistic Pro30 (modded)
6. Altec im716 (depodded)
7. AKG K240M
Of the other headphones I've had, none would rise as high as 3. The SR-5, K340, A250, QP85, QP95, DT990 and possibly Sextett would fit between 3 and 5. K400, DT531, HOK80-2, A130, and ESP6 would fit between 5 and 6. At around 7 I'd put the K260, HD560II, HD540, QP55x, SR-60, and maybe a couple of others I'm forgetting. Finally, the KSC-75, Ref 220, OVC T25, HD201, and a few others would fit in at the end, all good in their way, but as you can imagine not worth keeping around with the other gear I have and have had.
edit: the more I listen, the more I have to put the PMB500 at the same rung as the SR-Lambda. It's actually better than the Lambda for much of my music.