When grouping different components, are there any rules or rules of thumbs to use when stacking? Such as no power centers near the amp or preamp, or amps near cd players, due to interference. I need to place the following, what would be the ideal grouping?.....(amp, preamp, CD player, DVD player, power center)

if your gonna stack your gear on top each other,
make sure you have enough space between them so the heat doesn't get trap. If you have room,i suggest getting a stereo rack shelf >http://www.standsandmounts.com/index.asp?PageAction=VIEWCATS&Category=298