In my system, with my Harbeth's, the Hegel sounded dry and not very involving. The Ayre just didn't have the drive I was looking for. I really wanted to like the Ayre or the Hegel as they both have balanced inputs. I am also interested in the Ayre Codex which sounds much better via it's balanced outputs.
The Aria mates really well with the Treo CT's that I heard at Audio Connection. The midrange was outstanding as was the bass. I had thought you would need something like the Aesthetix Atlas or a tube amplifier to get a midrange like that on the Vandy's. The best integrated I have heard on the Treo's is the Ayre AX-5 but at $13,000 it was out of my price range. The Belles punches way above it's price point. I can't recommend it highly enough. I would try to go hear it before you make up your mind. I love the amp but everyone hears things differently and only you can decide if it works for you in your system.
I have had a bad experience with Heed so I did not even consider the Obelisk.