Originally Posted by khutch
The most common problem is that speakers are not normally designed to go that low so getting a significant SPL at low frequencies is difficult because of speaker limitations even if everything else is working right.
This is mostly true, but it depends on the type of tone you want in the lower frequencies. Obviously, if you want the fundamental to be the strongest component, yes, the drivers and cabs are going to have to be designed to be reasonably efficient at those frequencies.
OTOH, if the harmonics are more important (i.e. you want a more grunty, agressive, middy tone), you might be able to get by with what you have.
As for the bass, light gauge strings tend to exhibit more harmonics and heavier ones tend to give a better fundamental.
Those are the general rules of thumb, so experiment/adjust to suit.
Also keep in mind you're going to have to hump that cab to gigs; a cab that delivers well at 30hz (around where a low B is) is going to be huge and heavy.... So budget for some roadies in that case