Klipsch 5.1 Pro media ultra

Please help. My husband had a set of Klipsch 5.1 pro media ultra speakers for his computer. I broke one of his speakers and the volume dial. I am looking to buy a set off ebay. There is one going right now really cheap but it says they do not power up, but the speakers work. All I need is one speaker and the dial... What would cause the speakers not to power up? I do not know anything about speakers and I do not want to ask my husband because I am doing this as a suprise. Thank you for your help

Christine