I don’t know how big the diff would be between a pair (or quad) of 75hz and a mix of 75hz and 55hz. But the move from 90 watt Creambacks to 30 watt Greenbacks was significant - whatever bass Resonance. I’m sure your G12Ms sound absolutely killer. 20-30 watt speakers of any variety or flavor just provide some softness and ‘give’ to the guitar tone without adding any front end gain. Speaker compression is very different from amp compression and it’s hard to achieve with tighter, higher wattage speakers.