60 hz ? low level hum through speakers??????

i have a hospital grade outlet to a blue circle power bar to a blue circle power chord into my amp (yba passion integre) and kimber 8 & 4 tc cables going into a pair of spica tc 60 speakers. i get what sounds like a low 60 cycle hum through the speakers. i also have a monster cable power bar plugged into the blue circle power bar for the video stuff. and probably way too many cables crossing each other in the airmoire that all the electronics are housed. any ideas where this hum comes from? the amp? the speakers? the power set up? the crossed cables? turning on and off all the sources (cd player, dvd player, tv etc. seem to make no difference.