Upgrading crossovers is beyond my abilities
It's super easy. All you need is a screwdriver and basic soldering skills. Here's how:
1. In Norh speakers, the crossover isn't soldered to the speakers, it is screwed into the bottom with only one screw, so you can easily remove it. To get to the crossover, remove the woofer, then take out the crossover. Make sure you take note of which wires are connected to the woofer and tweeter, but it's very intuitive.
2. Once the crossover is removed, take pics and post it here. We can tell you which parts to order and where to order them from. You might spend a total of $100 or so.
3. Once the parts arrive, find a friend who can solder if you can't do it yourself. It might take 10 minutes per speaker to complete.
Here is a pic of the stock crossover in my Norhs. Yours will look similar: