If you want very low extension @ $1500 I think the Def Techs are going to be your best bet. Now if you can double or every triple your budget then we get into the realm of these beasts:
VMPS RM2 - ~$3000
Specifications
Bass: - 30cm (12") woven carbon fiber, 30cm (12") Passive Radiator
Mid: - two rectangular 10 x 20 cm (4 x 8") Neo ribbons, 280 Hz - 6.9 kHz
Treble: - FST, 6.9kHz - 30kHz
Impedance & Sensitivity: - 4 Ohm (3.6 min.) 91 dB/1W/1m
Power handling: - 300 W rms / 4 Ohms, 20 W min.
<strong>Frequency response: - 22 Hz - 25 kHz +0/-3dB</strong>
Dimensions & Weight: - 114H x 38W x 41Dcm, 55kg (45"H x 15"W x 16"D, 120 lbs)
Output levels and distortion: - max. 1% THD fullrange/1 W, max. 112+ dB SPL / 1 m
Finishes: - standard lite oak, dark oak
RM40 - ~$4500
Specifications
Bass: - 25 cm (10") WCF Megawoofer bass, 25 cm (10") WCF midbass, 25cm (10") Passive Radiator
Mid: - four rectangular 10 x 20 cm (4 x 8") Neo ribbons, 280 Hz - 6.9 kHz
Treble: - FST, 6.9 kHz - 30 kHz
Impedance & Sensitivity: - 4 Ohm (3.6 min.) 90 dB/1W/1m
Power handling: - 500 W rms / 4 Ohms, 20 W min.
<strong>Frequency response: - 24 Hz - 25 kHz +0/-3 dB</strong>
Dimensions & Weight: - 168H x 32W x 43D cm, 109 kg (66"H x 13"W x 17"D cm, 240 lbs)
Output levels and distortion: - max. 1% THD fullrange / 1W, max. 115+ dB SPL / 1m
Finishes: - standard lite oak, dark oak. Optional MLS african ebony, maple, birch, rosewood, walnut