moving from house to an apartment.. goodbye 802D's

I'd agree with the advice here to meet the neighbors and assess the specific situation first.
If noise is going to be a problem, switching out your B&Ws for a subwoofer won't save you! Unless the point is that a subwoofer can be turned off. 

The issue is that bass travels easily through floors and walls, whereas higher frequency sound is more easily arrested. My downstairs neighbor has an inexpensive subwoofer, and I hear the basslines through my pillow when he puts on his "morning music" at 6 am.

Jeez!  Just don't turn them up!

Thanks audio friends for all  of  the help.  I'm keeping'm!!

Did you consider a dipole subwoofer? It made a huge difference for my neighbors and I can now turn up the listening volume higher than before. You would get the added benefit of less boomy bass and more articulate bass than with a closed or ported sub.

Don’t get rid of your 802D‘s. If you love them definitely keep them. You don’t need to crank up the volume like a mad man and you can still enjoy music the way you are used to. Once you had a full size speaker there’s no way back to bookshelf little box.