Tom's P.A. Rack Details
For band gigs, the system is usually run mono; left channel as mains and right channel for monitors. This simplifies EQ setup for different rooms and allows the use of three way crossovers for the well built, home made speaker system boasting (for stage left and right) a 1x15" cabinet with JBL speaker and a 1x12" JBL spkr. / Altec horn cabinet. When run stereo, each singer's microphone is panned toward their location on stage but never hard left or right. Each vocal is still pumping through both sides, just less volume from one side than the other.
Sixteen channels have proven to be enough for almost every situation we've gigged in, and are probably the minimum required for any serious recording project where overdubbing is anticipated. You can do well with less, but it isn't as easy.
Rack / Power / Speakers / Mission Control / Monitor Amp