x2Resonant Engineering RE8 or RE10 should suite you nicely. Dual 4ohm coils, so they can be wired to 2ohm.
Don't have an insanely high sensitivity rating. But, running one of those IB shouldn't require more than 100w (if even that) to reach full potential.
Cerwin-Vega Vega 154Rated sensitivity = 96 dB
Efficiency (1 w @ 1 m) = 112 + 10*Log(9.64*10^-10*Fs^3*Vas/Qes)
Fs = 23 Hz
Vas = 181.2 liters
Qes = 0.39
Efficiency = 112 + 10*Log(9.64*10^-10*23^3*181.2/0.39)
Actual Efficiency = 89.4 dB (1 watt @ 1 meter)