It's an easy one for me - Mad Dogs are quite similar to LCD2. Too similar for me to feel the need to upgrade to them at the price multiple of the LCD2's over the MD's. HD650's are a kissing cousin to the Mad Dogs, can be had used at or under $300-ish on occasion, and are a nice, open headphone alternative to the closed Mad Dogs. I've also always liked the HD650 sound signature. I'd like to have a pair (or possibly the HD600 - I have never heard them though) for classical and the like, that do a bit better with an open can.
That said - if I was more able to use open cans than I am, the LCD2 would be a nice upgrade from the Mad Dogs, though diminishing returns really hits hard on that price/value comparison. The LCD2's are arguably superior, but they are open, and I think more than 3x the price.
The HE6 and HE5LE, and the HE500 all got my attention as well. Lots of cool open options out there. I really wish I'd paid more attention and gotten a listen to the TH900, Ed-8 and the AT W3000 Aniv, or whatever it was. By all accounts, I missed 3 very special closed headphones.
EDIT - I forgot to add that I spent a few minutes @ the Eddie Current table, and A/B'd the balanced LCD2 against my single ended Mad Dogs on that little balanced kit amp. They really, really sound similar. Very similar. I expected a more expansive sound stage from the LCD2, but it really was not, at least to my ears.
I also listened to my pair and all 3 of Mr. Speaker's pairs of MD's. They are very consistent. I could not detect a variation in sound across all 4 pairs. That really set me at ease knowing that one gets a consistent product when one orders the MD's.
The Ed 8 wasn't all that special IMO. Maybe it's me... but they sounded quite grainy at higher volume. Like something was clipping inside.
But yeah, what a pity. You missed the TH900 and W3000ANV. I'd say that if you don't want to spend your money on the LCD-2, then either of those 2 would be worthy upgrades.
By the way, there was an HD 600 at the meet as well. They sounded very much like the 650. Just slightly less warm, and with (markedly) less bass impact.
All this talk is making me seriously consider purchasing a pair of Mad Dogs now... Paycheck just came in as well...
I don't particularly care for more bass now, to be honest. The ES10 has shown me how much less of a basshead I am. But I certainly can appreciate a pair of cans that gives me more midrange presence than the ES10.
I gave in, Bill-P. Listening to them now