I'm not sure what you're looking for. Somewhere along the line you must have an amplifier. The advantage with using the optical out is that the signal is never transmitted in an analog form until after the amplification, so there is no amplification of analog noise. That is the best sounding solution - a separate receiver/amplifier that then splits into 5.1 (or more) speakers. You say you don't want that. Why? If you want surround sound, you usually need several speakers. There are "sound projectors" from some manufacturers like Yamaha that emulate 5 speakers in one, and then you can get surround sound from one box, but that's not exactly $100 solutions.
If you just want stereo, you can get some simple stereo speakers with a sub, such as the Harman Kardon Soundsticks that have very good sound.