Optical Out : What's in between the source and the final optical out?

I was having some difficulties in deciding which micro hifi to get.

Let's say both will eventually output everything to a Spherex speakers or some not so bad HTiB via optical out. Since there is no DAC involved, would they make any difference between the low end cheap and unknown brand vs the high quality ones?

Just take for example, the options are NAD C712 or Denon D-M35 vs some <$100 kind of hyundai micro hifi, however, it does come with an optical out.

so you meant the quality of toslink out is going to be the same for NAD C712, Denon D-M35 and the cheapo USD100 Hyundai brand micro "hifi"? wouldn't the CD transport make any difference at all?