Boltz sells modular component racks that are built like a tank. I think they are rated for at least 350 lbs. Just get the 14" spacing between shelves to provided adequate breathing room for your tube amps.
Another option is Michael Green Justarack. It's built with 1.5" MDF and 3/4" metal allthreads.
Michael
Another option is Michael Green Justarack. It's built with 1.5" MDF and 3/4" metal allthreads.
Michael