When I started playing some years back I made the common teenage assumption that doubling power was tied to doubling volume, of course most of us now know that all you really get is a slight bump in volume with double the wattage (3 db).
In pro audio the most common ways to maximize volume is to have multiples of the same speaker type, use electronic crossovers to split the frequencies before amplification or a combination of both.
Using any of the afore mentioned for a bass guitar rig adds far more headroom and efficiency then any single speaker or single amplifier could achieve.
Of course raw power is useless without great tone however you can get both without using over priced and exotic brand names.
My rig is fairly straitforward and consists of a Sansamp PSA 2.1 preamp with a rack mounted Lexicon effects unit in the send/return, this then feeds a Carvin BX-1200 (Bridged in mono @ 1200 watts/4 ohms) which offers plenty of extra tone and eq adjustments and is eq'd for mid bass/mids, this in turn drives an old Sound City 'upright' 4x12 PA column which has been retrofitted with (4) Eminence "Swamp thang" 16 ohm guitar speakers (4 ohms total). Using this cab with as little as 128 watts can deliever 124 db's, (over 130 db's at the speakers power limits) this added to the incredible tonal possibilities of the Sansamp pre, Carvin tone controls and the speakers natural tone offer 'tone nirvana'.
The Sansamp also feeds a very cheap Behringer parametric eq which filters out any mids and highs and is tuned to maximize the 30-100hz frequencies, this in turn drives a very powerful Crest FA-1201 power amp (bridged in mono) and bought on ebay for $250, this powers a simple 2x18' cab retrofitted with (2) Eminence Magnum 18LF (18" speakers)...overall this bi-amped 2,250 watt set up offers incredibly smooth mid tone with stunning intensity and lows that go beyond any 8x10 cab...on the down side this rig is heavy,has multiple components, takes time to set up, is difficult to mic and draws quite a bit of electrical current.