Ha, some good ones theo! I was thinking more literally. For example, the power amp or pre amp being the heart is nice in the lyrical, romantic sense, but I was thinking of it in the sense of pumping power to the speakers (just as the heart pumps blood to the body. The speakers and the body do all the "moving"). Speakers "exhale" like lungs do. The sources being the brain, as both are where the musical ideas come from. An a/c conditioner as the liver is perfect, though!
Heart, Lungs, Brains, Veins, Liver
What would you label your components if they were heart, lungs, brains, and veins, liver, Lets just go with speakers, amp, preamp, [cd player - record player ]. [speaker cables and interconnects ].