Hi, I have a friend who wants to build an inexpensive subwoofer. He only wants to spend a max of $125 and ideally $100 on the speaker and amp together, plus whatever it costs to make the cabinet. He's hoping to use a 12" woofer. Is there anything available in this price range? My first thought when he told me his budget was that it was a bit low and that he would be able to do much better if he was able to up it to the $150-$200 range, but I wanted to get some other opinions before I tell him that.