well wouldnt that be around the same price as a 400W HPS? and im sure they charge extra for puttin it all together for ya. dunno.
i know what your talking about the 660w thing you are talking about is just for the socket not the ballest. so you need a whole new set up. i made a really cool reflector/hood for my homedepot hps grow lamp the balest just sits on the floor with the old socket on a longr wire set. works like a charm.