Unfortunately, we also have such damn hard water. I do have a reverse osmosis system, but I simply can't manage it time-wise (self-employed and constantly busy). So at the moment, I'm sticking to bass, especially the Princess. I don't think I'll switch to soft water. Although... sometimes I get the urge and dream of redhead tetras, red neon tetras, or even better, Congo tetras.
280m x 80 x 80 is quite a size. How tall are you? Quickly cleaning the corner downstairs then slowly becomes criminal.
So I would definitely aim for an extra tech room at that size. But I wouldn't plan it in the basement. The pumps going through the ceiling would then have to be handled by special forces again. That usually turns out to be rubbish. I would actually plan it so that it's a separate room with a front into the living room. My program can only suggest that:
That's pretty cool. PS: What does your wife actually say about it?