In all my years of playing, I had never given any thought about mixing different speaker cabs. I always seemed to have a mixture. In fact, one of my favorites was a 80's Randall stack that was 2x15 and a 2x12. That being said, is the issue matching the speaker configuration or the actual brand of speakers? I have an Lds 4x10 and would like to get a 2nd 4x10. Lds picked up and moved to the Seattle area I'm told. What was once in my backyard is now far away and shipping seems ridiculous. How would I know what to look for? Or is any quality 4x10 the answer?