In my experience, a good DDC will almost always make at least a small impact on the sound. In many cases it will be an improvement, but of course there are exceptions, and in some cases it comes down to preference rather than a clear improvement.
The Aquarius has a really well sorted USB input and can sound excellent that way. For me, if I'm using it with USB I figure I might as well upsample to DSD as well, which again makes a difference that I personally enjoy.
If not using DSD upsampling, I like to use a good DDC and go with an AES connection. Have not tried the Musician DDCs but they look well done and I trust they are high quality based on my other Musician Audio experience.
Bottom line, the Aquarius is pretty versatile no matter how you feed it. There may be improvement to be had with a matching Musician DDC but it's not a guarantee, so definitely play around with options to see what you like best.