Always been pleased with ups booked with parcel2go when sending overseas
Being from Austria, I would advice that you make sure the parcel service can deposit your amplifier at a pre-specified place such as a kind of postal office - Mail Boxes Etc. offices for example or a person, somebody who has already retired, to receive the amplifier personally.
Otherwise it could happen, especially with houses, that carrier clerks drop it at the house without delivering it personally.
Could be that the amplifier disappears consequently but has been delivered officially.