You guys providing coastal source missed the entire point of his line with NE traditional home which cans any of the modern crap.
I hate to say it but your not getting around the inconspicuous. The only thing I can say is to have a few planters made up to house sat speakers (maybe out of cedar Latice) not sure what you could do with the sub, except maybe another planter on the ground.
On the other hand, why don’t planters work on the ground?
Www.planterspeakers.com