Interestingly Paul...
You
did say this, in the topic David mentions!
QUOTE
If you do have a really good PA that can handle the entire band, then at this point, you can look at turning down the amps and giving the band monitors. This gets their level up where they are, direct from the monitors, rather than from a distant amp going full tilt. However, unless the monitors can provide a few different mixes, none will be happy, still wanting to be able to get near their own amp to control the amount of general rather than specific sound. Only if everything goes through the system can the FOH people make it sound similar to what you hear at a pro gig.
Guitarists, can be a bloody nightmare, in some situations, and they can do something about it, weather reducing amp volume, getting Fx that simulates the cab etc.
As a personal opinion, which is based more around small stages, D Mills summed it up rather well on that other topic
QUOTE
Slap guitarist repeatedly (or better, explain to lead singer why they cannot be heard and watch them slap the guitarist).
Before I get beaten to a pulp by all the angry guitarists out there, I think I'd better point out that I am a guitarist myself