both ups & fedex have specific packing guidelines for electronic items,if you pack soley with packing peanuts both ups & fedex can deny an insurance claim should there be damage as they consider peanuts to be fill material & not a protective material.
you should wrap the unit in 2 inches of bubble wrap & put in the box,then fill any remaining space with packing peanuts & seal the box,then put the first box in another box that is 2 inches larger than the first box & tightly pack with packing peanuts.
if you dont double box an electronic item they dont have to pay for damage & the same goes for using packing peanuts as your only protection,you should only insure the amp for what it would cost brand new from the manufacturur to replace it, shipping companies will want estimates to repair or replace before they pay your damage claim,insurance is free up to $100 with either shipping company,after that its a small fee per every $100 of additional insurance.