[Plugin: Quick Cache ( Speed Without Compromise )] requires wp-config to be set to 777

That’s a weird requirement by the plugin indeed. Other cache plugins have either written to that file once per activation/deactivation or failing that, asked the user to do that manually. No other cache plugin has so far asked me to permanently keep the wp-config.php on any specific chmod.

Hopefully this gets changed with the plugin. For benchmarking information, WP Super Cache handles this part rather well.

It didn’t require that for me.