Using optical out...are all sound cards the same?

[veteq]

This is a new area for me. I am trying to put together a stereo music server. The motherboard in the computer has optical out rated at 24-bit/96kHz but the audio sounds very flat compared to CDs.

I will be playing mostly FLAC files and I am hoping to get 24-bit/96kHz audio quality out of the system.

Will a different sound card improve the audio out? even though I will be using optical out?

I am looking at using XBMC to play the music. any other recommendations would be greatly appreciated.