From what I've seen on the market, there aren't too many choices of footers (which purport to have anything in the way of isolation characteristics) that will support the kind of weight you're talking about. The Track Audio isolation feet are about the only thing I recall that say they both isolate and support the kind of load you're talking about. Otherwise, most rack footers look like they just change resonant characteristics rather than really isolate. Herbie's Audio may sell some footers that would work as well. You'd need to compute the load each footer would bear and contact them to see what they'd recommend.