Corner speaker for 604

[GM]

Isn't it desirable for the centers of the three drivers to be at the same height?

Would it be better to use a slightly smaller 606-like cabinet......?

.......why are there so few corner cabinets these days?

Yes.

Best to use a separate LFE system, so the mains only need to be just big enough to handle an 80 Hz XO.

Corner loading maximally excites the room modes, so a stereo pair creates strong peaks/dips in the response that aren't easily resolved in a typical rectangular room.

GM