If you're able to do easy woodwork consider building a diy Salamander clone rack. They easy to build if you're handy at all. The beauty though is that you can design it anyway you need and the shelves are always adjustable as equipment changes. Also they're very strong.
What Nrchy said above is a good reason to avoid stacking. Also the better you can get rid of the heat the more reliable your electronics will be assuming you keep them for years which many of us don't.
What Nrchy said above is a good reason to avoid stacking. Also the better you can get rid of the heat the more reliable your electronics will be assuming you keep them for years which many of us don't.