I don't know the US second hand market, but I still suspect you'd be left with more cash (and after much less effort) if you bought the spares, fixed the speakers, and sold them complete and working.
But you never know eBay - the complete amps and displays might go for some ridiculous price... anyway if you part them out, you will need to do more transactions and will still be left with a lot of parts that probably won't sell.