You could, but it probably won't have the results you are hoping for. When speaker systems are designed, even inexpensive ones, they are designed so that it brings out the best of the three main components: The crossover, the bass driver, and the enclosure size/dimensions and possibly the port (hole). If they don't match, bass performance will suffer big time.
So, you COULD replace the bass drivers but the odds of finding a better match than the original design called for is extremely slim. IIWY, I'd just save my money until you can get a better pair.