My current setup is an Ampeg SVT4PRO head with the SVT610 classic cab. I've played out with it a couple of times so far, and I can't help but feel that it barely has enough output. My ex-drummer, as well as my new drummer both play very loud. You never know what kind of issues you may run into with sound. I played a gig where people were telling me they could barely hear the bass. Apparently the sound guy decided not to run us through the house system. I'm sick of gigs being a crapshoot. A buddy of mine who's been playing bass professionally suggested adding a 15" speaker cab in addition to the current 610". He said it would provide the missing low end for the bass to be felt as well as extra volume. It makes sense to me. Both are considered "half stacks". The owners manual for the head shows how to setup up mixed cabs. I've brought this up on talkbass before, and people told me never to mix cabs at all. That it creates "phasing issues". Although from what I know people do it all the time. My buddy runs an AmpegSVT3Pro through a 410 and 15, and it sounds fantastic...better than my rig. Also considering selling my cab for another configuration. What should I do?