I don't know if micing your amp is a good idea. Considering your PA setup, I think the vocals will have a problem being heard clearly (for both the audience and the band). Maybe, you can convince your rhythym player to switch amps for this gig (seeing how important it is) until you can upgrade your rig. His Crate should give you a better sound and I'd think he could get by with your Peavey. Failing that, I definitely agree with loner about adding mids at the amp. I'm not familiar with the AX1000G; can't the patches in that tweak EQ settings for your scooped mids, etc. ?