Hi,
I know your thread is old, but I think I know what you experienced. The cd 7 sounded thin and un-dynamic. I used to own it, and I hated it and could not understand the positive rewievs it got. But as you know, ARC replaced it with the cd 8 quite quickly. Wonder why !
I own the ref. 3 and used to own a set of 210´s as well, and I had the combo you had as well, only did I use Wilson WP 7 at the time. I changed the cd 7 to a Wadia 381, and that helped. Later I changed to a Emm Labs CDSA SE. Much much better than the cd 7. So at the end of the day... Ref 3. and Ref 210`s ar very nice components in my oppinion, cd7 was not.