I found some info on
this page about sounds card hooked up to a cambridge home theater system.
I will copy and paste what page 2 says:
Before making the next set of connections, you'll need to choose which input to use for the computer or other devices and run the necessary wires. For digital connections, wires are included for all three interfaces. For owners of a SoundBlaster Live! card, Creative's proprietary digital DIN connection is made through two cables. One short cable adapts the digital minijack on the SB Live! to the DIN connection, and the other is an extension to get to the amplifier. For coaxial connections, included is a single RCA cable for connection to a Live! Drive, digital daughtercard, hardware based DVD decoder, or any other coaxial SPDIF connection. Finally, an optical cable is included to take advantage of connections to consumer audio devices, DVD players, or gaming systems.
Analog connections are via 1/8th inch minijacks. For four channel audio cards, there is a tandem minijack cable for connection to the front and rear speaker outputs. Also included is a stereo RCA to minijack cable for connection to the analog connections on consumer audio devices or gaming systems. It's unfortunate that analog connections are not available to the center channel or subwoofer as more and more 6 channel audio cards are available now to access these directly. But with its own decoder the system still offers full Dolby Digital decoding for surround sound.
Here is another
site to read.
I would go with a sound card that has an optical output and run that to an optical input on a home theater receiver.