Hi Ben,
You could use both the balanced XLR and the unbalanced RCA outputs of your Rossini DAC to drive 2 separate amps. Both outputs are driven independently in your Rossini.
The Blue Hawaii has 2 pair Single Ended RCA Inputs, so the balanced XLR outputs of the Rossini would go to your main 2-channel amp.
However, 20 ft of a RCA cable pair is not at all ideal, pricewise and for EMI ( Electromagnetic interference).