I mostly agree with Dave on this one.
There are differences in the electronics, wire gauges, metal types, processor chips, etc. If you listen to two sources (receiver, cd player, or whatever) that are different enough in their configuration, audible differences are not difficult even for a novice listener.
Although i may not be able to hear a difference between very similar components like an Onkyo 797 and a Denon 4802 receiver, i sure can easily tell the difference between that Onkyo and my 10 year old Technics.
