I have an early 2008 iMac, 20" 2.4ghz Aluminum. http://support.apple.com/kb/HT3470 The back looks exactly like this 2009 model. What I do not understand is my "audio input" as depicted in the picture. I've tried searching to find a simple answer. I just want to know if normal headsets (that come with two 3.5mm plugs for input/output) will work just like a PC. I have read in some places that it does, and others that it doesn't or requires a preamp of some sort? Any definitive answer?