If I'm not mistaken, your cab is 125W RMS (continuous). Before you go nuts with a rack solution (which will NOT be a solution, IMO), I honestly think you should consider replacing the cab with something more substantial.
No amount of effects or rack enhancers will make up for a cab that can't keep up at high volumes during a gig.
+1. The man has a point. No point altering the signal you put into a cab if the cab can't properly translate the signal into sound waves.