My Friend bought my KLH and Yamaha receiver. She will also buy the M&K later on. But for now I used her JVC shelf system subs (built on to the side of the speaker). I put one facing against the wall(sub), and then one upside down so it faces the wall.
Although the subwoofers are playing full range sound. Probally cutting off around 200hz. I turned them up alone and found no audible distortion and saw no harm to be done. The subwoofer played loud and effectively. It was perfect for what it was being used for. The JVC and KLH have about 10hz difference though. So there is a slight gap. But not bad for a temp replacement. The Yamaha if you are wondering is pushing the subs and the KLH's off the main amp. *Smart* huh? I didnt notice the receiver getting rediculously hot. We will see. Thought I would share this idea if you ever run into it and want a temp replacement that sounds half ok.