A lot of advice about getting the noise and bits perfect BEFORE the DAC. A cheaper option is to add a fibre cable BEFORE the DAC and do not worry about what comes before the fibre.
Someone above posted about the PlayBack Deigns streamer that has a glass cable, well that is fibre. I actually owned the Playback Designs STREAM-IF and that also supported fibre but only for PDB dacs (non-fibre for other DACs).
A few weeks ago, I gave a local audiophile a $20 fibre cable that he plugged into his HiFi Rose streamer. It was connected to about $200k worth of gear. He is keeping the $20 cable and told me it was a great upgrade.
Put the fibre just before the DAC and forget about what comes before the fibre. I think this approach is starting to gain some momentum based on the posts I read online.

