I also find the Sundaras and the HD600 family of cans to be an excellent companion to each other. No need to have one over the other, if one can swing it they are a great compliment to each other. Can't wait to add the HD660s to the family, just waiting for the right deal. Happy listening!They really can adapt to different eras (Led Zep / 80's / Radiohead) or if a favorite artist makes a drastic change in their sound. Those are the times I'm really looking to use EQ. I was able to make a few small changes to the "oratory1990" settings to get what I liked out of a rather obscure 80's album and it sounded great. I wasn't so enthused about it prior to that so I sure did appreciate that.
The Sundara is a great companion to the 660. You could get by with the two and maybe just mess around with amps and tube rolling. They both can reveal good detail and cover a lot of bases.
Other than just pure curiosity about the 600/650, I'm starting to look at amps based on the performance of these entry level cans I've got so far. I do kind of have a boner for Focal or LCD2 headphones but I don't know about them yet.
Thanks for the reply. It confirms some of what I'm hearing! lol