I kind of agree that soundstaging is mostly in the recording, but just like other things in the recording you need a system that can bring that out. Separation and resolution and detail...I would guess these are all things necessary to convey width and depth to a soundstage.

The amp matters but so does the source. Don't ask me why this is exactly, but my Apollo resolves detail and separates instruments much better than my 650BD. Of course, one would expect it to but it was quite alarming for me to actually hear the difference.

Many say metal domes are too harsh. I had a pair of Energy C-1 speakers that used a metal dome and didn't find then to be harsh at all. But I had a pair of Monitor Audio RS5 that I found to be too much. The conclusion I drew was that if a speaker employs a metal dome, perhaps it's a good idea not to bump up the frequency response in that region. Energy measures quite flat, whereas MA does not.

I think both driver and cabinet size play a role. Floorstanders get their fuller and bassier sound through larger cabinet volume often with relatively small drivers, but I think a larger driver can provide a more effortless sound and of course will move more air. But doesn't the choice of size largely depend on your room? I found the Monitor Audio RX2 to be way too much speaker for my small room, and the rear ports surely didn't help.