I do not know the answer to this just yet, but it's a damn good question. Going to do some searching to see if I can find anything.
The fundamental problem with using the souncard of a PC as a H701 replacement, as far as I can tell, comes down to 2 things:
A. Software (which should be relatively easy for someone with the right programming skills to remedy, I think). and
B. A serious lack of RCA outputs for a competition system (I worked out I need a bare minimum of 5 stereo channels, 6 would be better, and an extra mono above that even better still - thats between 10 and 13 RCA plugs).
1st question: Can one of those Digital/Analogue Converters (DAC?) provide multiple RCA Analogue outputs from a single Toslink input?
2nd question: If so, is there a limit on how many Analogue channels per Toslink cable?
In other words, is it possible (theoretically at least) to run all of your digital processing, EQing, X/O control, Volume adjustment, control for individual speakers, and anything else you happen to need through the PC, then run the output out via a clean digital signal through the Toslink to a (DAC?), which then splits the signal into its respective Analogue RCA outputs, and to run them into your existing amplifiers?
If the (DAC?) can't split the signal that way, what about amps with digital input? Could the digital signal be split into multiple channels in digital?