Hello Snidely,You could go 1.5" but it is a pain in the rear to have to laminate all the wood together plus cutting 1.5" of MDF is not fun.
I decided to comprimise and make my cabs out of 1" MDF.
Yes you need to make the boxes larger if you go with thicker stock.
Two of the same resistors in parallel makes half the resistance and twice the power handling.
Go with 16awg inductors......