"If that is correct it is way too much power for the SI 18's.
They are rated at 600w RMS.
Wouldn't these be overkill?"
well, that might be jumping to conclusions."Indeed Stereo Integrity confirms that the power rating for this driver is based on the mechanical overload not what the coil will handle thermally. They recommend 600w and no more for this driver. The very compliant suspension results in little power being needed to move the driver to full stroke. SI's recommendations for this woofer make sense in light of this and the driver will not make much use of more than 5 or 600w of power without getting into trouble. Depending upon the particular enclosure design more power could possibly be used but careful measurement and simulation would be needed to assess the wisdom of applying more power."
folks are running those subs with that power with no problems and great results. just don't put full power sine waves on them. that is abuse, not use.
"Also wiring for a 2ohm load will increase distortion thus increasing risk of damage to the drivers."
if the amplifier distortion rises from 0.1% ot 0.2% that isn't going to damage any drivers. full power clipped blasting might, but that isn't so much related to distortion as it is sending direct current through the driver.