full range and woofer question

Hey, im new to the car audio scene and I have a question. I have a citroen c5 that i want to upgrade sound system on a budget and I also have speakers from factory upgraded jbl system but when I connect it (tried factory radio and 2 external amps) it sounds muffled like its playing in the other room. Both configurations also had tweeters but they didn't really help that much with jbl sounding muddy. Is it a problem where the original speaker is a full range driver and the jbl one is a woofer or am I missing something?