Don't necessarily blame the speakers. It could be the amp is feeding it a poor quality signal. Garbage in Garbage out. You could try upgrading the amp first to get a good signal to the speakers. I changed my AMP and the difference is remarkable. I still want a SUB but the improvement is significant even with the original speakers. Doesn't matter how good the drivers are, they aren't programmed to convert a bad sound into a good one. At least the OEM speakers are designed for the space they are in.
How a look around this forum there are plenty of opinions and good ideas about if you dig around a bit.

Oscar