Shipping 80lb amps.

Use a freight company double boxed and on a pallet as others have recommended. I would shy away from FedEx and wouldn’t even consider UPS. UPS is extremely rough with heavy fragile items and their claims department is thoroughly indifferent and will string you along for months and try to pay you next to nothing. I say this because I know from experience!

Use FedEx and insure accordingly. Carefully double box with extra padding.  No need for a pallet.

As I have shipped well over 12.000  boxes in the past 20 + years,  I can definitely state that they are all the same.....UPS / Fedex / DHL,  etc.

2 problem areas:

1.  the centers in which any box will be handled and thrown around multiple times,  and

2.  ultimately the driver itself....he who doesn't give a shti is working for all of these companies.....

Any insurance co-writers of these companies have the 200 lbs per square inch impact  /  policy for the shipping boxes.  If there's damage,  and the boxes are not rated at least 200 psi's then the insurance companies (which are a nightmare to deal with anyway...deny, deny,  deny) will definitely walk away from their obligations.....   All of our boxes are indeed rated the industry standard 200 psi,  but you should check before hand whenever you ship anything.

Also,  it is  true that any box will lose rigidity after it's been shipped at least 1 time,  so yes,  all of the advice above about double boxing is a good one.....and even double boxed,  make sure that the outer box is also rated at 200.....these MF's are really peculiar about this number.....

Good luck,

Klaus

Carlsbad is correct. 
Do not allow buyer to arrange shipping nor payment and to deal with the shipper, that is, use his (buyer’s) account. Insurance will not cover anything shipped to oneself. 
 As a seller, YOU arrange and pay for all shipping costs. Of course, buyer can reimburse you if agreed. This is the only way you have you have a chance at an insurance claim. 
You sold it. You ship it. You pay for all costs. 
I’d pay close attention to Klaus’ advise. He’s the man. 
Good luck. 

Use a freight company, palletize and strap the amps onto the pallet then shrink wrap over it so nothing can be placed on top of it.  Fragile stickers can also help.  Most importantly double box the amps.

Good luck!