i assume you worry the speaker are having higher power than it should?

the gain will do the trick by multiplying the correct power to the tweeter.

Crossover is just to limit the frequency range, it reduce some power but it's not a proper power limiter, it's a range limiter.

So, sum up, yes u can use the 4ch amp to power the 4 driver, adjust the gain correctly and you will be ok. Power doesn't really kill the driver, the range kill it mostly.