I shipped an amp that weighs even more than that to the East (Classe DR3 VHC) but had an original double box. It came back in good shape via UPS, although I was worrying the whole time it was away that some idjit would drop it off a loading dock.
If you don't have an original box for it, suggest that you contact Simaudio and see if you can buy one.
If you don't have an original box for it, suggest that you contact Simaudio and see if you can buy one.