Some American told me long time ago that all HD receivers have to have the firewire-interface enabled. I would suggest trying to copy them 1:1 via firewire (there is a software used for D-VHS once in the internet).
The best solution would be to copy them natively directly from the HDD.
The third best option (and the first for me) would be to buy the set on BD (it's cheaper now). It think the price is lower than any other solution involving hardware you don't have or that doesn't work (and requiring to buy additional gear).
In Germany the PayTV providers try to force people into getting their own boxes, which generally are not only nuttered in terms of functionality but also have of a very bad quality, both constructional and reliability. I own my own STB and I could always recover the recordings from the HDD. Movies I don't record, as usually they have various issues (senders' logo, less channels, lower A/V quality, lack of subtitles, lack of the original audio). This is what I recommend to you, too. It will be a good future investment, a movie can be remuxed and authored (chapters, subtitles etc) within one hour, if needed, in original broadcasting quality.
Coming back to your question, S/P-DIF should be in theory possible with all soundcards having digital in. The software has to bypass windows (
ie it has to be ASIO based) for best results (or any results at all
). Many freeware and payware can do this. You can even create a graph to save the digital stream to a file.