Notice too that sensititity is proportional to wattage ratings. Often, within a manufacturer's lineup, the sensisitivity rating goes down (up numerically) as the amps get bigger. Often, there's a difference in ratings between balanced (XLR) and single-ended (RCA) connections, when that's an option.
Gotta admit that those Meridian 605's are mighty sensitive for 150 watts.
Generally for a passive, the output of the source is critical with at least 1.5V and an output impedance less than 200 ohms being favourable. If there is an impedance mismatch, frequency extremes get rolled off.
Most resistive passives are about 10K input impedance but 100K are available, including some Noble pots which is the brand reported to be used in the Axiom. Higher impedance is an easier load but there are trade-offs.
Then, speaker efficiency plays a part too. So does the length and capacitance of the cables....
What was your question?
