Great advice by everyone.
He's my .2 cents (with repeats):[LIST]
[*]Move the guitar amp away from your kit. Can you place it a little behind and at a angle from your kit?
[*]Get the bass amp close to you and near your bass drum on the opposite side of the guitar amp. Having you two in sync is key and should be top priority.
[*]Get a small 10" - 12" monitor and place it close or just off to the side of you. Guitar Center always has them in their Used section.
[*]Get a couple $50 instrument mics and put them in front of the guitar/bass amps. You could also put two mics in an X/Y pattern on a boom stand just over your drums. If you mic the bass amp and it's placed close to your bass drum, it should capture some of your bass drums sound too.
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Not sure about the availability of funds, but about $100 from each member would really give you some flexibility with the mix and volume control. Also keep an eye open for Guitar Center 20% off coupons too.
Not sure how many inputs your PA has, but this type of setup would require about 5 to 6. Doing this might even give you more control with the feedback issues.
Hope this helps, good luck and keep us posted.
- Tim