How much improvement with better toslink cable?

What Sufentanil said.

You might want to try an Amphenol glass cable just to put your mind at rest. There is a source for these if you to a search for Amphenol in discussions.

I believe I did detect a difference going to glass, but you must make that call yourself with your system.

Glass toslink make a huge improvement over regular in my opinion. I have detected almost zero difference between cheapo and branded non-glass toslink, but the upper end Audioquest and Wireworld supernova 5+ toslink will stand out far above the standard toslinks.
I have no experience with the amphenol.
I am a dealer, but do not sell any of the brands mentioned in this reply
good luck

What Buff said. Don't understand why Toslink is so quickly discarded as I've heard it sound superior to coax on more than one occassion.

I can tell a definite difference when using a Virtual Dynamics Master digital cable in my system on some recordings.

I cannot tell any difference in clarity, but I like the way the VD cable presents its sound stage differently. To me it seems that each instrument is not only in its own space, but that I can focus in on each musicians feelings of the music. I don't get this on all cd's, but I do notice this when using the Virtual Dynamics cable. This probably sounds absurd to some of you, but I can tell the difference and I know it is not just about the ones and zeros.