7550 would be more boring but I actually loved those. Ex1000 was too sibilant but otherwise amazing. I thought the 600 was a baby 1000?
I had the 600 and the 1000 at the same time. They sounded almost exactly the same to my ears, with the 1000 having better resolution. One night I grabbed the 600 thinking it was the 1000 and it took me several songs before I realized it.
Recently when I was going back and forth on what to get, the 600, 7550, or 1000 I saw the 600 for like $120, but I waited too long and someone snapped it up. But it worked out since I got the 7550 for a good price along with the EX1000 cable.