If it were me I'd look into either upgrading your speaker components or going into better ones. Once I heard the difference in drivers I upgraded to Volti Rivals that use a much higher quality 15" driver, and much better mid/tweeter drivers.
Changing just the bass driver in the La Scala would be a large upgrade, something that changing your amp won't do. But once you do that then you'll look at crossover and other drivers and so trading the whole thing up is what I decided.
Best to you!

