OK all you speaker experts. Here's a small question for you. I under stand speaker impedance and wattage ratings with no problem. I have recently, much to my delight in my quest for more knowledge of the bass and bass amps, discovered "efficiency" ratings. The efficiency part is a new concept to me. After all these years of playing, I never really thought about it before, but have seen quite a bit on it recently. It would explain why some cabinet combinations have worked better than others with the various cabinets I've owned. How close should the SPL rating be between two cabinets that are to be used together to enable them to function reasonbly close in the sound that they provide? I am looking to match a 1x15 cabinet with my Ampeg SVT-410HLF. It is 4ohms, 400W RMS, with a sensitivity rating of 99db and a max SPL of 125db. I know it will need to be 4 ohms, in the 350W to 450W range, but how close would it need to be in the SPL? I don't care if it has a horn/tweeter or not. I will not be using it alone. So, I guess I'm looking for a real efficient 1x15, 4ohm, 400W cabinet. Thanks!