Got the HD650.. again.  This is the third pair I've owned.  You'd think I'd have learned after the second pair.  Nope.. I'll get the obligatory statement out of the way: I won't sell them this time.

but I probably will.. cause something "shinier" will catch my eye (another round with the HD800, perhaps?)..

and then I'll regret it..

and then buy a fourth pair.

It's inevitable.

I. am. idiot.

Chain yourself to the 650's and then put on a blindfold.
If Sennheiser comes up with yet another revision of the HD650's I'll buy again (although I have the latest one atm)!
^that is unless they turn the 650's into crap like momentums, urbanites, HD630VBs or something (highly unlikely but you never know by looking at the last few headphones/in-ears they made).

@purr1n, have you considered testing your new HD650 with an older one?  Mine is 4 or 5 years old, and I'm curious if any other changes happened when the packaging changed...

My first pair were the updated drivers, but sound a lot darker compared to the ones I bought last fall. The newer ones seem to offer a more linear response; instead of having an overall emphasis of dark, rich mids, the treble of the new ones sounds much more resolved.

It took a month or two, but I now much prefer the newer pair. Not sure if it is simply pad wear, or the clamp that is causing the difference. It is quite a contrast between my pairs though. I also found the clamp naturally eases, to the point that after three months, I'm glad I didn't fk with the band to lessen it. The old ones clamp far less.

I Feel like the HD800 + HD650 could be my end-game and would surely cover all bases for my music enjoyment.

That combo was my endgame for a while, but I got frustrated that I had to swap depending on genre.  Ended up selling off the HD800, living with the HD650 until a new flagship came out that could give me all the wonderful technicalities of the HD800, with just a little bit more warmth and smoothness like the HD650.  Now that I have a better source (Pulse Xfi + LPS) to pair with my Bottlehead S.E.X. I almost don't miss the HD800's.  Almost.

Nah, the 600 and 650 will never be turned into crap. Look at Porsche. Purists cried foul when the Cayenne SUV was introduced, saying it would ruin the 911 in the process. 13 years later, the 911 is still the 911, and that's not going to change no matter how many suburban mommy-wagons they sell. Sennheiser is following the money right now. It doesn't mean they are completely abandoning the reputation they have built up amongst audiophiles and music lovers.

I hope so. I heard they will release a high-end open back not too far in the future. I hope they will come up with another great like the 650 or the 800. But then heck, the 800 is still so hard to get the best out of.