Unless I'm missing something in your question, I would think that one of the Bel Canto DACs will do just what you are looking for (1.5, 2.5, 3.5). They have volume controls, can act as a preamp and have optical inputs.
Since you list Bel Canto as one of the options that your remote works with, this should do the job for you.
***Bel Canto dealer disclaimer***
Since you list Bel Canto as one of the options that your remote works with, this should do the job for you.
***Bel Canto dealer disclaimer***