The amp appears to have been driven hard enough to show the rails. If the amp produces clean audio, I'd use it as is. What else do you think it needs?
Problem I am trying to solve is that it overheats and turns off when playing at high volume on a hot summer day...
It comes back to checking the biasing at high temperatures. If the bias is holding at or near thermal shutdown, I'd suggest adding a fan blowing over the heatsink.