i've heard that sometimes if an amp comes on after the pre amp. it may give a popping sound... some people use a delay to avoid this happening.

funny, but not all systems have an issue with this. I've never had any issue of amps popping. For some reason it appears the Marantz MA500 amps i use have some kind of 2 or 3 second delay before they kick on. and i don't get any kind of popping at all.