Pardon the self-serving post, but this is a pretty unique solution: I have a laboratory vibrations isolation table that weighs about 250-300 lbs and can accomodate a large turntable. I used to use it for my front end system components. It is made from lead and steel - I can't imagine anything more rigid or high-mass / high-density than this. You can get a glimpse of it in one of my old system pics here on A'gon. It works fantastic for isolation, and is suspended on four shock-absorbing springs, one on each of the corners. I've tried to find information online, and found similar tables for around $2,000. These are passive tables (except for the springs), not active as the Halcyonics solution seems to be. Well, mine is currently in storage because when I moved out of my studio (work space) my wife would not allow it in our small house. It is seriously heavy...not a one-man moving job. I noticed you are in Portland, otherwise I would not suggest this...I'm in Seattle: If you are interested I've been considering selling it. Ping me off the thread. It is not something you'd want to ship. Regardless, it is another possible solution if you can find one. They are used in physics labs. Their WAF rating is well below zero...we're talking divorce-level approval ratings here. Also, you'll need some good, strong friends to move it around. One friend would normally do, but once they help you move it they A. won't be coming back a second time, and B. may not consider you a friend anymore. Hence the need for more than one. It is certainly a conversation piece as well. Don't even think of mounting this on the wall.
Marco
Marco