Having used both the Apollo and Cambridge Audio Azur 840C extensively, I can say that the sound between them is rather different.
Big assumption: The DagMagic would be along the lines of the Azur's sound. It is very likely you would see an improvement. However, I agree with Mapman that a tube DAC would further distance you from the Apollo's sound (Likely in a very positive way).
Finally, do not skimp on the Digital cable for the DAC as it has a strong influence on the quality of the resultant sound.
I have used the Monarchy M-24 pre/DAC with several players acting as transports. I used the Rega Saturn with the Monarchy and it was superb, a very rich upgrade in warmth and nice expansion of sound stage from the Saturn alone.
So, I would think that the similar transport of the Apollo would similarly be vastly improved by a good outboard tube DAC.
Big assumption: The DagMagic would be along the lines of the Azur's sound. It is very likely you would see an improvement. However, I agree with Mapman that a tube DAC would further distance you from the Apollo's sound (Likely in a very positive way).
Finally, do not skimp on the Digital cable for the DAC as it has a strong influence on the quality of the resultant sound.
I have used the Monarchy M-24 pre/DAC with several players acting as transports. I used the Rega Saturn with the Monarchy and it was superb, a very rich upgrade in warmth and nice expansion of sound stage from the Saturn alone.
So, I would think that the similar transport of the Apollo would similarly be vastly improved by a good outboard tube DAC.