I remember North Creek Audio and he liked to use Scan Speak speakers.
Most all production speaker could use a crossover improvement. Top of the line crossover components will get very expensive. It also depends on the number of drivers weather it a two way or 3 way crossover. Capacitors depending on the type can get very large depend on the value and the material. Flat wound inductors also can be costly. It all depend on the speaker. Most common tweeters were 104 mm front bezel and there are many options for that size.
Good Luck