PC Streaming Audio Help Please

PC streaming audio advice. I just signed up with Spotify Premium and in preferences I checked HI-Res streaming and Hardware Acceleration. I purchased an inexpensive PC audio card (audiodeck 24HF) with Toslink output and acceleration ability because when I first hooked up my PC and tried to use it’s coax output, I introduced a groundloop “buzz”. Now the system via the soundcard in my PC is connected by Toslink. The Toslink cable I settled with after trying a few has 280 Glass fibers with a mirror polish, it’s a no-name cable, 12 feet long and picked up for $29 from HDTVhookup.com, it has demonstrated to me that Toslink is a viable option as it sounds great, and there lies my question.
The inexpensive audio card is via Toslink connected to my Cambridge Audio AZUR 840C CDP is performing a reclocking and upsample to 24/386, the sound card is sending a 24 bit 96Khz (it’s max) signal to the AZUR and as I said it really sounds good, but can it be better? I was toying with the idea of upgrading the soundcard to something that can send a higher bit rate, or maybe a card that has an isolated coax connection, but I have no idea what card to purchase and am looking for suggestions. A big question I have is do I want a card that sends out a higher rate sample rate or do I want to actually send the lowest rate where the much more sophisticated CDP handles all of the up conversion?
Your thoughts please!! Thank you!