HELP! 2008 prius touring audio issue

I have a 2008 prius touring with the jbl system. It has the 3 plug jbl am under the passenger seat. The car was hit on the passenger side and both passenger doors were replaced before I bought it. When they replace the doors they did not change the speakers back to the jbls, The front speaker and tweeter have very little volume, like next to none, they are playing but are barely audible at full volume. The back wasn't even hooked up. When I did hook it up, it plays but sounds terrible. I'm thinking I should go ahead and get some replacement speakers but I don't think it is my only problem. My question is , Can I replace or easily add a decent amp near the old one, seems easy to add since all of the wiring is there? Also I hooked up another speaker to test the front right, It was an 8 ohm home speaker but was also very quiet, so I'm guessing the problem is in the wiring or amp? thanks in advance!