Some amps like the TAD Hibachis in my 2 channel a/v system have output level adjustments on-board which can be very effective for providing left/right balance when needed for whatever reason.
Placing speakers to match volume levels is probably not a productive approach as you have found. Placement is key for soundstage, imaging, bass levels etc. Placement to match loudness is likely different than placement to optimize these other areas where placement is the key.
Placing speakers to match volume levels is probably not a productive approach as you have found. Placement is key for soundstage, imaging, bass levels etc. Placement to match loudness is likely different than placement to optimize these other areas where placement is the key.