^ Do any powered speakers in this class have a volume pot that's accessible when the speaker's used as a floor wedge?
They all seem designed foremost for FOH PA duty, so it makes sense that there's no attenuator on the speaker side, tempting under-inhibited audience members to give it a whirl. Still, having the attenuators on the back of the speaker doesn't offer useful on-the-fly volume control when they're used as monitor wedges. (And frankly, except when you're running your own sound, you probably don't want the wedge's attenuator within reach of the singer during the performance.)
JBL PRX cabs have a level knob, but are outside the budget parameters. We use my PRX 612Ms for monitors and they work great. The OP may be able to find some used PRX 512Ms at near the budget price.