For your arm choice, just get the Schroeder Model 2, it will be a lot better than any of the other choices.
Between the Denon and the Shelter, its a matter of personal taste. For the Denon, a little more care is required with the arm setup and the phono gain as its a low compliance design. Frank Schroeder has a brass plate mount for the 103R and you'll be fine. For the Denon, you will need >60db of phono gain due to the low output.
I've not heard the Shelter, so let others comment.
Between the Denon and the Shelter, its a matter of personal taste. For the Denon, a little more care is required with the arm setup and the phono gain as its a low compliance design. Frank Schroeder has a brass plate mount for the 103R and you'll be fine. For the Denon, you will need >60db of phono gain due to the low output.
I've not heard the Shelter, so let others comment.

