@Avanti - In my system I can only compare to my Rega Apollo CD player, but of course I have heard many other good digital sources.
The Art-9 is pretty much the opposite of dull/dark in my system. I bi-amp and have the ability to adjust tweeter vs. woofer/mid levels, and one of the things I have in mind as a possible tweak once I get some time on the Art-9 and begin to mess with it is to knock down the tweeters maybe just a hair. Not sure if it will be necessary, but from what I am hearing now I certainly don't think I'll need to bump the tweeters up.
I haven't heard a really good Art-9 as mine is not broken in or optimized yet so I don't have that perspective, but from what you describe you and I are hearing different things from a "new" Art-9.