Your speakers have blown. They are paper cones after all. I replaced mine with 10cm Alpines. You won't get much "extra punch" in such small speakers. What's annoying is that there isn't any other speaker with the same spacer holes. 13cms won't fit, so you will have to go with 10cm. I'd spend the money on the front speakers where I think you will notice the real difference, although knowing Toyota, you may have to make your own mounts.