I have two enclosures hanging from the tower. Each enclosure has two 8" midbass drivers and two HLCD tweeters. Each cabinet weighs roughly 25-30lbs.
The tower itself is still solid, even with the speakers hanging from it. As long as no loud music is being played, its fine. It's just when the midbass hits at a high volume I get a resonating like sound. Putting my hand on the tower and applying pressure did not seem to help the noise.