Without trying the Denfrips you are likely not to know. What is the difference in sound between streaming and your CD player? If there is a big difference with the nod to the CD, then getting a streamer and getting your laptop out of the loop should provide a large improvement in sound.
About connections. Typically the quality of the component (in this Case DAC)… is many times more important than which connection you use. Having said that the USB is a much newer connector added to allow streaming from PCs. It wasn’t that many years ago DACs had no USB inputs at all. How good a USB connection sounds depends very strongly on how good the streamer is and the DAC… simply put the signal from the USB source needs much more processing than any of the other connections.
I would choose a separate streamer and use the AES connection or SP/DIF. Optical is nearly always inferior. Streaming can sound as good or better than a CD… a better DAC should improve both. Denfrips are very highly regarded.
