If you store in a basement, be sure to get them at table height or a leaky basement could be a disaster. Cheers,
I've seen basements that had relatively high humidity percentages that would warp (severely) veneer wood finishes and open up corner joints in otherwise good speaker cabinets. This could happen even if the speaker was inside a carton off the ground. Any kind of storage can have good or bad points. IMO
I would suggest getting some 'Damp Rid' or similar product. sealing the units in containers, or bags and then in containers.
its absolutely astonishing how dust and critters will get into 'left alone' stuff in perennially dark seldom entered into places. even when they appear to be firmly taped up in their orig cartons!
then later.... they'll act as if they were new all over again, requiring a stint of run in once more.
I'd opt for a closet in the house proper first. basement second. and never in an attic.
the notion about keeping them up off the flooring some is a great idea. JIC.