Welcome to the boards Phillipe,

These woofers should work great with the WO. I just ran the numbers in WINISD and they should work with the original plans (no need to mod the sealed side). The difference in the 36" and the 24" will be low extension. The larger box will play considerably lower and sound more "musical" in a home. If you are building it for car use, it will simply have a lower overall tuning. In a home, the lower tuning tends to sound better, but in a car, the higher tuning can sometimes reach higher SPLs. That depends on your goals and the application.

I would definitely wire the subs in series and bridge your amp. This not only presents a better load on the amp, it will also provide the same drive to both sides of the "horn" and make for smoother output.

Build it, you'll like it! I guarantee it.

Take care,
Robert