We tend to have problems as the amps and drums are loud!

Until you address this problem there is no magic fix. Turn down the amps, use a hypercardoid or headset on the drummer's vocal, minimize bleed.
The best thing to remember is that an audience wants to hear vocals ABOVE all else. Start with that in mind. Use mics that make the vocals sound good and build around that.

Ideally, you should EQ (especially on the Mackie) only as needed to roll off some bass or adjust for the room.

Your post may better be served by the Live music forum - Gaff?

You are not gonna want to hear this, but you are probably gonna have to turn those amps down, for starters. A JCM 900 can inflict great damage, and the El Diablo...! Anyway, try keeping the amps and cymbals from getting into the vocal mics. The drummer should probably be using a headworn mic to minimze bleed-through of his kit. the other vocal mics should be at least a Shure SM58 (cardioid), but a "supercardioid" is even better at feedback control (Beta58, some Audix OM models). A "hyper cardioid" actually has slightly better rejection at its sides, rather than the back, so this will determine where you "aim" your monitors. Those Peavey "sound-on-a-stick" speakers should probably NOT be on their stands during rehearsals...I'll bet you have them aimed at the players' heads, right? Try putting them on the floor and aiming them UP at the "null" spot of the mics instead. Use something like a cinderblock to lean them up at an angle during rehearsals may help. If they're on their stands and aimed at your heads, they're also firing at the "hot zone" of the mic. Firing them up at the back of the mic may help. Finally...DEADEN THE ROOM!
Use heavy blankets or moving pads to keep the sound from bouncing all around the room. Try going to "Markertech" (google them) and seeing what they offer in heavy blankets and other acoustical treatments. Diffuse the sound, too. Those fiber egg cartons glued to the walls ( or to panels you can lean against the walls) will do wonders to break up the sound.
As far as EQ is concerned, try rolling off some of the bass, boost a LITTLE of the 12KHz for presence, and play with the mids (boosting will very possibly induce feedback). You only use EQ as a LAST RESORT! And don't let the drummer or the bassist tell you otherwise! I've done live and recorded sound for over 30 years...EQ is never the answer (well..)!
BTW, you're not really thinking of using those little PeeWees on a live gig, are you? :)

it's your drummers fault. :!: You'll have to get rid of him :twisted:
Seriously though, anything with a volume knob will get turned up to the loudest acoustic instrument. For practicing why don't you sing through one of your guitar amps and force the guitar players through the pr12's and eventually the drummer will figure out the wonderful world of dynamics.

Just a guess, I'm sure you'll figure something to make everyone happy with their levels. 8-)

Thanks so much for all the help. This will definately help me out. I guess we'll turn down the amps. I have suggested to the drummer to get a headset, but he doesnt want one for some reason, I'll keep nagging him. I'll put the speakers on the ground like monitors. The practice room is carpeted with lots of curtains, but also wood paneling on the walls. I use a Beta 87a, a couple of the guys use sm58's and the other two use crappy samsons. What would you suggest be the best speaker combination for small gigs with a Mackie 808s?

Well, something with a little more kick than the PVs...Yamaha has a "Club Series" that uses castframe Eminence 15s....they will handle more low end and move more air. The low-end JBLs should be avoided at all costs-they use stamped frame Eminences and cheesey horn-drivers. Some Mackies are OK, especially the 3-way active models. Basically, for FOH, you'll need something with a 15" castframe woofer and a titanium 1.5"throat horn driver...