PCI-e Sound Card

Ok im in dying need of a PCI-E (internal) or USB (external) for my new mac pro. Reason being is that my sound system cant be connected by optical.

Speakers go into sub and sub has 3 ouputs, green black and yellow (one for front, one for surround and one for sub) that usally just stick into a normal soundcard but i cant find a surround sound card anywhere for my mac pro.

Any suggestions?

Sorry for sticking it in this section too, wasn;t sure where to put it and its more likely to get a better response in here

thanks