Best DAC for my situation...Read on!

So thoughts and opinions please.
What I have and my idea.
Oppo 105D and Bluesound Vault 2 feeding into McIntosh C48 preamp.
I chose the C48 because it is a nice complete all in one box solution, headphone amp, mm and mc phono amp, lots of analog inputs with 2 sets of xlr inputs AND 5 total digital inputs.
Now I have both the Oppo and the vault connected by analog and digital inputs to the C48 so I can compare modes pretty instantly and I have to admit both cases the analog sounds better.
Which makes me wonder if the C48, although a great all in one solution may be the hold up as far as the DAC performance is concerned.

What I was considering as a trial is a seperate DAC that can handle the digital signals from the units and then output the analog signal via xlr preferably, back to the C48.
At this stage I have no intention of getting rid of the C48 as I really like the analog signal SQ as well as the headphone performance.

Any good suggestions in the range of $2000 used or am I really not going to see much improvement at that price range over the C48 capability?