SUB in Apartment

I don’t think it would be a problem as long as you keep the Sub and bass level at a lower setting and you don’t use it late at night. The great thing about the Sub is you can easily disable/enable it in the app under the Sub Audio setting. But of course it will also depend on the people living below you. Everyone is different and can react differently to hearing bass coming from the apartment above them. Some people are obviously more sensitive than others.

Mostly it will depend on the construction and sound insulation levels. If you can hear your neighbours walk around - I’d venture a sub might annoy them. I live in a terrace house - but modern build with very solid walls and I can run 5.1 with  2 subs at louder level than comfortable to listen to in the room - without the neighbours even knowing. But I’ve lived in other places with poor construction where that luxury was not the afforded.  And as said - also depends on the people. I have an arrangement with my neighbours to message (sms) me to turn it down if it gets too loud. They have only done so once when I tested how loud the whole house would go (22 units at 80% volume).

Could be a case where it would  be worth you buying from a source that has a good “no quibble” returns policy so you can try it out and see what happens. Good luck. 

Movies with effects are likely to disturb, as may bass heavy music. The Sub also adds richness to music that isn't bass heavy, where it is less likely to cause trouble. So this also depends on the kind of listening you will use it for.

Something to consider in addition to the good advice posted here already.