What do you mean "optical output to feed .wav files to my amplifier" - That makes no sense.
What equipment, specifically, are you using? Are you looking for a recommendation on a music server of some sort?
If you are, then the Bluesound equipment is often highly recommended as a purely streaming device. Likewise, you can get things like Sonos which work well, but Bluesound seems to get the nod for great quality.
optical output to feed .wav files to my amplifier
I assume you then have a proper AV receiver of some type which you are using as a preamp/amplifier to take in the Toslink connection.
I'm not sure where you are storing these WAV files, or where you are getting them from, but you just need a network streaming device with a reasonable interface. The bulk of what you buy will be about the interface you get, which will dictate the ease of use. It will actually be a smaller part of the expense which goes towards the hardware itself. Any digital audio, streamed throughout your home, should come out of the playback device with excellent quality.