The speaker is a transducer type which means it needs to be in contact with another surface (typically) to produce audio. They sound okay, at best, and are mainly used because they can be completely invisible within a room. They would be best for background audio where aesthetics matter more than actual audio quality.
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I would not use it, but would sell it if you can via Craigslist/eBay.
The C28 is like an A/V receiver except is has not amplifier built in to power a speaker, so an external amplifier would be needed. It is a VERY dated piece, but if it is working, will bring several hundred dollars via eBay.
If I wanted good stereo sound, then perhaps keeping the C28 might make some sense, but you would need good speakers and a good amplifier to get the most out of it. Not exactly an inexpensive way to go for a newbie. Instead, I would sell everything if you can, and use the cash towards a few new products if you are interested in getting into audio/video.