I made a prototype from some affordable components. The look was suitable with our other products and the amp section worked great, but the premade crossover section was behaving badly. So I am back on the search for a reasonably priced crossover/control stage. To aid my research I have ordered, among other things, a switchable low pass filter from Harris Labs (50Hz or 70Hz) that should arrive today. If that works out I will suggest it as a possibility for folks who might already have a suitable power amp with level trim to use with the passive sub. In the meantime I will continue to pursue a kit subwoofer amp product that is in line with our visual aesthetic. Things will move a bit slowly over the next week or two as we are jamming to get out all the Black Friday and Cyber Monday orders, doing a normal month's worth of kit packing in little over a week.