Originally Posted by joecaption
Trouble is adding and not removing would throw off all you floor to floor heights, every doorway, where the dishwasher is if you have one.
The OP stated he's not doing the kitchen nor bathrooms which are tiled, so no issue there.
From the OP's description, it sounds as if he added a "plywood" subfloor in the "wet areas" as he called it and then tiled it. If that is the case, those areas should already be quite a bit above the original particle board subflooring. He therefore should be able to make a smooth transition via t-molding reducers/transitions after adding a second subfloor and then hardwood flooring in the rest of the house.
You make a solid point though and all that is something the OP will need to consider. The OP will of course need to undercut door casings and trim some off doors in making everything work, but that's common.
Take care, Ralph