I have tried a number of different transports and dacs and currently run two systems with digital separates.
Firstly, I have found that a jitter reduction device such as the Audio Alchemy DTI Pro will improve the sound of most transports. I also disagree with the comment above about transports not making much of a difference in sound quality.
For a toslink cable, I would recommend the Monster Lightspeed 100. Some say the 2 meter sounds better than the 1 meter, but I have not tried that. I have tried the Lightspeed 200 and the lower priced 100 is better.
For dacs, I would avoid the Cal Gamma. I have read a lot of good things about the Sigma and have just bought one, but have not received it. Dacs to consider if you want something small would be the Bel Canto or Micromega (Duo BS or Microdac). Micromega's can be bought used fairly cheap.
I have not tried a Sony ES changer as a transport, but I know of one high end dealer that used to recommend them for customers buying high priced dacs that insisted on a changer as a transport. I use a Stan Warren modified Aiwa changer as a transport and it is a good transport, but not as good as a Parasound single play belt drive transport that I also use. If I had not stumbled across the Aiwa, I would have gotten a Sony ES to try.
I have not tried a lot of changers.