It is good to see a speaker DIY project and I presume you are still waiting for the ordered parts to turn up? If so, can I suggest you
read this thread and take some care.
The K100 has extremely expensive drivers but they are good ones. If you are happy to pay the price then that is sorted.
The cabinet is a large single one and will need both internal stiffening and effective damping adding to the walls. Stiffening the front baffle would also be good but is less important. If you are not opting for the flat pack and fitting the internal stiffening and damping yourself I would suggest discussing with WA what can be done.
If you read the the link above you will see the crossover is basic and lacks the refinements related to baffle diffraction and driver bumps and dips that might be expected in a speaker at a high price. In truth the high quality of the drivers makes this less of a problem than it would be with more modestly priced ones but it is something to check and keep an eye on. The OP in the link above was not able to resolve the issues with the crossover WA delivered for his speaker and for him the project failed after a lot of faffing around.
I am not trying to put you off but suggesting you check and perhaps prepare one or two things while waiting for the parts. The speaker you have opted for is pricey but if implemented well is likely to be pretty good. If the passive crossover turns out to be less than ideal then fixing it is a significant but not a major task and there is a fair amount of DIY experience about with your set of parts.