My vote :
Theta
Meridian
ML 40
Halcro ? I have not heard, so I cannot comment.
I tried others as well, some were mentioned including the flag ship Krell, Anthem, Bryston, Arcam and Lexicon. As good as these were they are not in the same league. The review was done at a dealers upstairs room, 5 of us played for hours. This was a real eye/ear opener for the staff.
The Krell Standard 7.1 which won over the Arcam and Bryston was brought to my home to try against the Anthem and Theta. The Theta won in all aspects.
The Meridian dealer would not allow for it to be tested/evaluated against the other gear.
First as we all know theater technology changes quickly.
With most companies you have to buy a whole new unit vs upgrading.
Knowing this I find it hard to support a company that does not allow me to upgrade the pre-pro once the new formats is available and widely accepted.
Both the Meridian and the Theta have card slot type upgrade boards which makes it very simple to keep up with technology. I would not want to have to change my pre-pro everytime a format changes.
This is why Theta and Meridian stand at the top of my list.