Great to see you got them up! If the main photo in the stereo listing is a stock photo, you should remove it. Items that are used shouldn't have stock photos. I would also use the full 80 characters in the title. At the very least, add the brands.

If someone was searching for a Kenwood subwoofer, they would have Kenwood in their search. Yours may not come up in their search results, unless they tick the option to seach the description as well (most people don't tick that box). The title doesn't have to make sense, but you want as many keywords there as you can fit.