My current setup is my new iMac in the living room and I have a hi-fi connected through an airport express in the kitchen. At the moment I am able to play music on the computer or send it through airplay to the hifi in the kitchen. I have my old iMac currently setup in the spare room upstairs and would like to know if there is any way I can add the old iMac to the wifi network so my iTunes in the living room gives me the option to play music on my 'Computer', 'Kitchen' and also to play music on the iMac in the spare room. Can this be done>