I have a mid-2011 27" iMac, and I have connected a set of Logitech Z-5500 5.1 speakers to it via digital optical cable. Although it doesn't compete with my home stereo system, the sound is quite impressive. In particular, when playing music, they provide a form of "surround" that is quite nice. I have a buddy that has almost the same iMac. He likes my speakers and wants to setup something similar. However, Z-5500's, even though no longer in production, sell at a premium price. I got mine for under $200 many years ago, but I've seen them online now going for anywhere from $500 to $1,000. Does anyone know of any other 5.1 speaker system that will work with the iMac (since I'm assuming the only way to connect them is with the mini toslink cable)? I'm assuming that the Logitech Z906 speakers will, but they're a bit out of his price range, too. I'm wondering if any of the cheaper models would work. Would they work as long as they have an optical digital input and have built in DTS/Dolby decoding? Thanks for any suggestions.