Thread: Onboard sound via Optical Vs add-on sound?

Well my Streetdeck trunk bundle currently has a SB X-fi music card I just picked up a DSP unit with optical input and was considing switching to use the on-board sound via optical to remove some of the bumps and moans in the car power system

I get a little whine at start up till windows boots up and int's the sound card then I am rock soild quite no noise no hiss no whine at all figured with optical I would be a bit better anyone every listened side by side and noticed any differance between on-board optical vs add on analog?