How much of an improvement are new speakers>

Kind of a generic question. I bought a 01 Civic, so far Ive put in a panasonic 250 watt cd player. Just wondering if I spent maybe 150 bucks for new speakers, would these speakers be a big improvement over the factory ones? Im asking this because I once bought really good Cherwin-Vega speakers for my 86 Audi Quattro, and they were not an improvement over the old factory ones, in fact, the Vegas were worse. Just wondering how good the factory speakers are on this car. (They dont seem that great to me.)