First of all, in regards to your original post, NEVER have the amp sent back, as that will void any insurance that you purchased. Always contact the shipping agent and they will send out their inspector to investigate and pick up the damaged item.
Second, you should be alright in claims if you use the original manufacturer's packaging, or have the item packaged by an authorized shipping agent. If you pack by yourself and do not use original manufacturer's packaging, you might as well save money on the insurance, as you will never receive any damage claim. Do not over insure, as the claim will only be processed to the amount that you can prove that you received for the item. This is to keep folks from ripping off the shipping agents by shipping damaged goods that they sold for $500 and insured for $1000 from making money at the expense of the shipping agent. Yes, sharks are everywhere.
Lastly, I have received full insurance payment for damaged goods when the box was undamaged. In my case it was a power conditioner in the original manufacturer's packaging (I always keep the original packaging). It was determined that the damage was caused by a "flat drop". In this situation, the box could be dropped straight down from a height of 6-8 feet and fall completely flush on one of it's sides. In which case the box could show no signs of visible damage, but sensitive electronic equipment inside could still sustain damage. In my case, the glass meter cover cracked. I was refunded the full amount. Good luck.
