Noticed this weekend while out on the lake that the tower speakers sounded awful, upon closer inspection I found out why. (pictures below)

1) Should I only replace the broken 2 or replace all 4?
2) How do I find speakers that are the correct size and correct power for the amp?...

Hello Team Talk, I got a problem. I have a tower with 4 speakers, 4 speakers in the boat, and a stereo. The speakers in the boat work perfectly, but the tower speakers don't make any noise. I originally thought that I needed another amp to support the tower speakers. But, I looked and my amp doesn't...