You could also buy a QAM tuner (assuming you're tuning digital channels with the TV.) If you're happy with your TV's current channels, the QAM tuner should have outputs for audio to hook up to a surround sound system.
Although then you're at the whim of the cable company if they decide to encrypt some of the channels, but then again, you'd have the same issue with the TV alone.
Don't believe everything on the Interwebz! A duck's quack DOES echo!