Yes, but expecting a small box like the Obelisks to reproduce convincing low bass is, er, optimistic. I actually quite liked them, not too bad at all. Taking off the wheels might help the muddle in the middle.
Performing structural alterations to the house in order to try to get one's speakers to work properly is an interesting approach!
I doubt I will fiollow Alex's advice and fill the cavity under my floor with concrete BUT that said the floor is a bit loose, the house is 70 years old and nothing has ever been done under the floorboards. I may try stregthening the spars (not the right name I know) that go under the boards. Anybody tried that?