Not that it really matters, but what car do you have? Stock systems aren't really worth a damn thing. You'd be better off keeping all of it, so if you sell the car you can put it back in and keep your new stuff.
If you really need the money then put it on ebay, here, or the parts trader and see what people offer, but I would keep it in case for some reason or another you sell the car and want to keep your new stuff. You won't be getting that much for the stock stuff.