First, I would make sure your subwoofer cable isn't damaged - in fact, I would expect that to be the most likely cause of failure the first time it broke too. Do you have any spare cables laying around that you can swap out?
Also, have you tried calling Klipsch back to see what they say about it?
Btw, there is EQ built into the amplifier for the RSW-15....just a straight up amp swap isn't going to get you back to where you were...
~It's all about compromise~