In general, with 2-channel home audio (as opposed to A/V surround sound which is different) I have observed people with tube amps are more likely to add subs to add value to already full range speakers.
That is because high power quality tube amps, if needed, are big, heavy higher maintenance, and expensive, not something many will want to have to deal with.
Whereas Class D amps in particular provide a user friendly cost effective option to drive subs or full range speakers with lots of watts and current needed to make them sing to their best.
If one is interested in sub arrays to better balance the bass across the room, then that is a different story with a different goal in mind, but personally I would only go there if desired once the usual issues common with all two channel hifi are addressed and system is tuned in from top to bottom including bass initially at the "sweet spot".
Also if main speakers do not have adequate dispersion (something I know Duke of Audiokinesis, who is an authority on bass arrays, I believe, cares a lot about) and thereby capable of tonal balance across the room to start with, achieving that with just the bass may still be desirable but is not a total solution.