I don't know too much about amplifier and cabinet specifications beyond knowing how to calculate the Ohms an amp head can handle. What is the relationship between a cabinet's SPL rating, its wattage rating (RMS) and how much volume it can produce? For example, will two cabinets with the same RMS wattage rating put out the same volume when the SPL rating is different? Or do you need more "juice" to get a lower rated SPL to sound as loud as a higher rated SPL cab? And if so, will the RMS wattage rating limit restrict the overall volume it can produce?