I like how the iMac has decent built-in speakers considering that it's an all-in-one. However, I'm looking to get external speakers for my iMac. Originally, I was fine with getting a 2.1 system just to get better sound quality compared to the built-in speakers but I think I will go all the way and get a 5.1 system. So I'm not necessarily looking for recommendations for a 5.1 system but I do want to get some clarification about the iMac's external audio capabilities. I know that if I plug in any external speakers into the iMac, that I will get stereo audio out of the 3.5mm headphone jack. And I know that the iMac has optical out in the same jack. However, after looking through Apple's site for tech specs, it doesn't say anything about being compatible with 5.1 systems. Ultimately, what I'm asking is, is the iMac truly capable of delivering 5.1 audio? If it is, what exactly will I need?