Problem is, many original packing boxes are entirely inadequate. I think many packages are designed to be shipped palletized in a large bundle and that's a different kettle of fish from shipping a single item. Marantz, Cambridge, & PS Audio are brands I've bought with woefully poor transport boxes. UPS says packaging needs to be stout enough to survive a 4 foot drop onto bare concrete, so think about how that relates to what's needed for a heavy amp, etc. I'm lucky in that I have access to very good packing materials through my job and I make most of my own shipping boxes from double wall corrugated cardboard. I glue the corners with wood glue and reinforce them. As Elizabeth mentioned, surrounding equipment with foam of adequate density is vastly better than bubble wrap. It is hard to source unless you have a Uline store close by and it costs too much. If you do use bubble wrap, use the heavy duty variety with fat 1" bubbles, not the thin stuff with 1/3" bubbles. Peanuts have no place at all in packing heavy audio equipment. When I need to fill the space between a double box, I use pieces of expanded polystyrene sheet that's used for wall insulation.
