There's no single correct low B gauge. S.I.T. makes low B strings from .110 to .140, and which gauges are available depends on the string line. With comparable construction and scale length, a heavier low B generally feels firmer than a lighter one. The right choice depends on your scale length, construction and preferred feel.
A heavier low B doesn't guarantee more low end. It changes the feel and can affect output and response, but pickups, technique, setup and the bass itself all affect how much low end you hear.
On an extended-range bass, also check that each string's winding length and taper location fit your instrument.