I believe JKenny's mods to the M2Tech Hiface offer an I2S output. There appears to be a new model from M2Tech that offers it out of the box, but I cannot find much info on it. Properly implemented I2S to a DAC would improve your chances of a quality transmission, no? It would avoid the issues that SPDIF has by skipping it entirely. You'd need to find a DAC with an I2S input, but they appear to be out there.
--Matt