have you tried running one
2x15 cab, wired for a 4Ω load, like a normal sane person?
if you're dragging out four 15s and feeling like you're not loud enough, something's not right.
a single good 2x15 with good power behind it should be as loud as any drummer, which is all you should ever need in bars/clubs;
conversely, any room or stage big enough to not get swamped by four 15s should also have a big enough PA and monitor system for you to do fine with no bass cabs at all