If you're willing sacrifice surround for decent stereo and use other switchboxes/switching solutions for the picture, you can get by on the cheap by picking up an old stereo that supports external signals through RCA. With a bit of luck, you'll get both decent speakers and some kind of equalizer.
Like Futureman2000 mentioned, there's also the computer speaker route. Some of the more expensive PC speakers have digital/optical sound in through toslink but most don't. However, 2.1 sets are usually very simple to hook up to a TV. Simply plug it into the headphone jack - works brilliant!
If you're willing to spend the money, there's also the old surround reciever/stereo amplifier way. Digital/optical sound through toslink/coaxial seems pretty common on the ones I've seen. I use an older Denon amp for me PC and a big Pioneer thing for me games. You should be able to get all the inputs you need and a few more, but you'll have to pick up some used speakers - and those will likely cost more than the amp if you're after anything good.
The good thing about that kind of setup is that it's very flexible, and not only will you be able to upgrade your speakers later on, but also add a subwoofer (usually active ones, from what I've seen) of some kind and possible also more speakers, like a center one.
As for the cost of this, my PC audio setup costed about a $227~ plus some more for cables and stuff.
And that's for amplifier/reciever, stereo speakers, center speaker and active subwoofer.