Here is my reply to Earle in response to an email he sent to me.
In my experience, from a purely sonic viewpoint, re-foaming is NOT an option. They will sound crap!
The foams are MUCH less pliable than the original flimsy rubber material, the result is restricted travel of the cone and subsequent change of sound characteristics of the woofer.
$180 per speaker! I suppose if that is per tower then I could probably understand. If that is per driver, it’s a rip off.
Calibration is not difficult. It involves feeding the completed speaker with an audio signal of specified frequency (100Hz if I remember) and specified voltage and thereafter adjusting the voltage output from the amplifier to accommodate a more/less efficient driver. The adjustment is performed by removing a set screw from the face of the heat-sink fins and adjusting a trim pot with a long screwdriver.
All the replacement drivers that I have fitted have had a sticker stating that their output is +0.5dB.
Replacing both drivers would mean +1.0dB from the completed tower which to my ears gives a pleasant and much needed boost to the bass.
The choice is yours!