Shipping 80lb amps.

"Instead box it so they CAN'T break it."

No such creature. I once shipped a four foot by four inch diameter x 1/4 inch thick stainless steel pipe. UPS took the challenge and bent it. FedEx lost one of my Harbeth 30 monitors even thought shipped as a pair and labeled box one of two. The humor in it was they knew which warehouse it was scanned into, but could not physically locate the box.

Double box with double wall boxes, palletize, label "no top load" & "fragile" on all sides and insure it to value. Then photograph all sides.

Don’t ship anything in a box or case with a handle on it. With a handle, it’s like a personal challenge to the handlers to see how far they can throw it. I have seen dramatically less damage to items when any handle is eliminated. This even includes a Pelican case in which the handle was sawed off for such a reason. 

Ship on a pallet! I shipped an 85 lb amp via FedEx. It arrived at the buyer with a circuit board detached along with a capacitor. The box was intact with no damage. I guaranteed it was dropped to sustain that much damage.

FWIW I have made it a policy to bring my sold items to the UPS Store or Fedex/Kinkos and pay them to pack.  They use lots of bubble wrap and very stout boxes and I've never had any problems...but my shipments were not 80lbs. 

Have you considered Class D amplification?  Lighter for sure.  /JK

Be careful to insure each box for the full value of the pair if you ship them that way, unless Klaus would be willing to make you a single matched amp to replace one that is trashed.