The DSD stream is always in encoded format, so you cannot mix equipment from different manufactures. Another misunderstanding is firewire port. Physically this is the same port in PC and DAC, but on a computer it is used for another purpose than on dacs. So, summing things up, it is not possible to connect ANY dac equipped with firewire port to any PC based server with firewire port no matter what you do.
I suggest going out from your PC with digital PCM signal thru AES (the best) to the dac. You can also use wordclock feature if you use Lynx or similar card, which will make jitter lower. Also, you can use upsampler (like dCS Purcell 2nd generation, or Paganini or Scarlatti) and upsample from PCM to DSD format and then route this via firewire cable to dCS DAC (Delius, Elgar Plus, Paganini or Scarlatti). This is the best for the moment in my opinion.
I suggest going out from your PC with digital PCM signal thru AES (the best) to the dac. You can also use wordclock feature if you use Lynx or similar card, which will make jitter lower. Also, you can use upsampler (like dCS Purcell 2nd generation, or Paganini or Scarlatti) and upsample from PCM to DSD format and then route this via firewire cable to dCS DAC (Delius, Elgar Plus, Paganini or Scarlatti). This is the best for the moment in my opinion.