Briggan The Wolf
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Right next to Mississippi Records, there is a small store called "Mississippi Home Stereo" that is owned and managed by Eric (or is his name Aaron? I don't know).
It's filled with, of course, home stereo equipment - receivers, amplifiers, speakers of all shapes and sizes, record players, a few radios, and parts/components. Just about anything you can think of. The prices may seem a little on the high side, but that said this is a small, local business running on sales income - and I fully support that. And unlike eBay or online marketplaces for buying used audio equipment, you have the privilege of testing the equipment (or asking Eric to do it for you) and making sure it works - and works properly.
When it comes to buying items, you usually pay cash (I don't think he takes credit or debit cards... haven't tried), but if it's an easy sell or returning something you bought from here, you can get away with exchanging a piece of equipment and pay less for the gear you want.
As for repairs, you might as well hobble over to Jamac Audio for speakers unless it's a simple fix, or if it's a record player. Eric's repair team is short-staffed and so he has way too many projects going on right now. You might be able to get a job opportunity there if you're handy with servicing audio gear.
As for selling, I haven't sold many pieces of gear, only speakers. So I can't really say anything about record players or receivers/amps. That said, Eric is interested in decent speakers - ideally with real wood veneer or walnut, not vinyl, if it needs work. If it doesn't need work, I'm sure he'll take most any speakers. Just don't expect to get much cash for it.