Money-wise the best thing you can do is sell the XLS and hunt down a pair of DX9's.
Tweaking or rebuilding the crossover is going to cost you, possibly a lot of money, and it adds no resale value to the speakers. If you get the work done and still don't like the sound, you gain nothing.
I was given sage advice a couple years ago when I proposed modifying some speakers of my own: if you don't like how they sound, the cheapest option is to replace them.