I'll answer part of your question and leave the rest to other brave souls.

If you're using your CD player simply to read the digital information off of it and pass the digital data stream to another component, then the hardware you use makes no difference. In other words, the digital output on your soundcard (optical or coaxial makes no difference) will sound the same as the digital output on a $2000 CD player.

The analog outputs are a completely different story.