How do you know the amp didn't fail?
How do you know it's the speakers?
However, the 1400 Watt amp will melt 500 Watt speakers.
And so you need speakers rated 1000 watts each...
You can take the blown speakers out of the Mackie cabs, and replace just the speakers, with better ones. You can reuse the cabinets.
Maybe you need a pro sound tech, to help you do it.
In any case the power comes from the amp, not the speakers.
You can use 1000 watt speakers, 1500 watt, whatever you want.
But I would consult pro audio dealer for replacement drivers...so you know what you are getting is the right application.
In any case, you don't want to run the amp bridged, into 4 ohms...that's asking for problems.
You probably want to run it stereo, left right.