i ahd a 15" D3 and I didn't like it. If you want something from diamond audio get either the D6 or D9 and make sure you give it a lot of power and in a ported box tuned around the fs.
actually i have a friend who has 2 12's sealed with a 900 watt kenwood amp and it doesnt sound too bad but for the price they are good subs mo but you can look int cvr's typr r's assasians all in that range
i would rather buy new u never know what u get from ebay. i bought some stuff from a guy with a 99 percent positive feed back and it was the wrong stuff so im done with e bay