Okay, it is an 8 ohm driver and they're already installed so make the best of it. IOW, don't drop any more dough into them if you don't have to. With a little thought and judicious EQ'ing, I'm sure they'll sound decent enough for the project at hand.
Power amps / watts be cheap. What's your budget? With the advent of newer technology w/ competitive pricing, the older lead sleds can be had in the $100-150 range...I'd be hard-pressed to spend more. I'd aim for what I term a "1400" amp: one capable of kicking 1400 watts in bridged mono / 4 ohm. This would include the QSC RMX 1450 and Mackie 1400i amongst others. If you can find something with more power at the same price, snag it. If you can spare $400-500, there's plenty of new gear available that will fit the bill. Check out QSC and Crown (Drivecore). I run my PA rig in bridged mono and daisy-chain the mains.
"...my whole body's a weapon" - Luther Heggs