Make the drummer play softer and turn down everything. Seriously. He can practice his hard-hitting playing on his own. Band practice is there to practice playing with other people, so unless you have a great sounding PA and a good room, just turn it down. If you are not a medium-level band you'll be playing small clubs anyway and a drummer who is not that loud will be worth his weight in gold there. My drummer is extremely powerful, but he plays really soft if the situation needs it. Sounds MUCH better in smaller clubs!
Also: all of a sudden you'll start hearing all the mistakes.
my thoughts exactly.
we're using a comparable setup (2 vocal mics, trigger, behringer mixer, can't recall the poweramp right now though) and there are zero problems with the PA being too quiet.
aside from the advice quoted above, make sure your guitar amps are dialed right...the sounds should compliment each other. use less gain, more mids, so your sound becomes more punchy and cutting at a lower relative volume. (yes, mids are good, even in a death metal band

)
regarding the PA, be sure that the mic input gain is set right. enable the low cut on the mic channels. on the trigger, use a sound that's mainly click, with little to no bass thump - remember, there already IS a fat bassdrum being played in the room, so all you should use the trigger for is some top end click to make it more audible and cutting. you'll need much less volume this way.
set up the Pspeakers correctly, i.e. not on the floor, and be careful not to have your vocalist directly in front of them (feedback!).
if you follow these guidelines there shouldn't really be the need for a big EQ imho.
live sound (even band rehearsals) depends on basically the same things as studio sound....you have to make space for each instrument to sit in, so that things are complimenting and not fighting each other.