Most likely one of the capacitor died considering the age. If you can find local electronic repair shop, they probably can just replace the caps and resistors with exact same value and you'll be good to go for another decade.
IMO you would be hard pressed to find better system at $500 mark. Cheapest AV Receiver is already $300, not including Subwoofer, center speaker, front speaker, and rear speaker which could easily another $200 EACH ($800 total).
Edit: I'm not surround guy, but me personally Center Speaker + Front Speaker is more than enough for movies. My Wharfedale put out more bass than I already needed, so I also don't run any subwoofer.