Several years ago we did some in-house testing with polypropylene caps versus other types. The sonic differences were amazing. Good quality caps and good design also enable higher power handling systems. We check the voltage and current limits of all of our passive crossover designs to make sure they can withstand full rated power and then some. Impedance compensation of the load that the drivers present to the crossover is something we have been doing more of on our higher end systems.
Some amps have a very hard time driving a load that is highly reactive.
That is to say, more capacitive or inductive than it is resistive. If the amp doesn't like the load, it can have a lot to do with the sound quality. This means that for some of the large venues, the line array reverts to a point source when you're sufficiently far from it. Used properly though, line arrays can still be very useful. Just don't use a horn to do it.