I was asked what sort of surround sound speakers to get for an Apple Macbook. These have a combined optical digital audio output in the output/headphone minijack. They therefore don't work with cheaper models of 5.1 surround sound speakers, which require a sound card with multiple analog plugs. Some of the more expensive home theater systems have optical input, but these tend to have a built in DVD player, increasing the size and cost for a PC addon.
A useful alternative seems to be a set of USB surround sound headphones.