Folks,
It is a shame when equipment arrives damaged although the packaging should be adequate for the job. However, I would caution people that "should be adequate" probably isn't adequate.
There are 4 potential pitfalls for proper packaging: 1. shock absorbsion, 2. Package penetration, 3. crushability and last, but not least 4. movement.
If you don't package an item (especially a heavy one) without considering all of these pitfalls, you will have damage (sooner or later).
Many people think that styro-peanuts of bubble wrap is good enough, but if an item is heavy and is dropped, neither of these will sufficiently prevent movement of a heavy item because of the inertia of the item. The box corner stops when it hits the ground, but the amp doesn't because it has considerable inertia. You absolutely must prevent the amp from moving within the box.
As Vinnie stated, using specifically cut styrofoam layers is your best bet. Make sure there is enough to completely encapsulate the item you are hoping to protect. I buy 1/2" pink styofoam (with backer) from Home depot. I use a drywall "T" as my guide and measuring device and a utility knife to cut it. Works great! I also make sure that there is enough foam around the item to completely prevent movement. If you can jiggle the box and see/feel any movement at all, you're not done yet! If you need smaller pieces than the 1/2" foam, use layers of cut cardboard as filler. Use the cardboard as the layer on the outside edge of the box and it will also increase the ridgidity of the box and improve the ability of the package to prevent penetration and crushing.
I've shipped electronics probably a hundred times via FedEx ground, UPS and USPS and I've yet to have a single item damaged.
Not preaching, just offering some unsolicited advice.
Enjoy,
TIC