I would think there could be some level of "Micro-vibration"going on with the cages installed. Unless there are kids/pets/housemaids...etc...leaving them off adds the final benefit of tube amps (besides their sonic attributes): they are sooooo coooool in the dark or dim light....ssooooo coooool. I always leave them off and actually gravitate toward amps where they are in full view (all 'performance-else' being equal) just for "The View".
SSSSOOOOO CCCOOOOOL.
SSSSOOOOO CCCOOOOOL.