Hi Brian...
I have a set of BOSE901 series II. I'm assuming the newer versions follow the same build parameters although with newer drivers and equalizers.
I believe the Bose901 drivers are 6-8 ohms each and thru use of proper series/parallel circuit wiring will ultimately show a 6-8 ohm total load to the amplifier. They are not 1 ohm each. Be sure to follow the internal wiring connections within each cabinet.
The front driver is the same as the other drivers in the cabinet.
I don't envy you having to do 18 foam surrounds... Good on you.
Graham