Least cost way to send amp to USA from Belgium?

Talk to Bax Global all the same. They might collect it from your workplace or you could drop the package at their offices. Customs is a problem of the importer in the US, not for you and it will depend how you declare the object. I've sent a few things to the States back for repairs or modding and declaired the goods accordingly. It was never a problem. Cheers and good luck,

Have you considered the good old US Mail? I would choose Air Parcel Post. (Regular Parcel Post takes forever if international).

Depending on how much the amp is worth, it maybe wise to ship it UPS Priority (guaranteed 2-3 day service) versus Expedited. It will probably cost double but will spare the unit of extra wear and tear during shipping. I had a pair of speakers shipped from Europe (90 lbs each) and it not only took eight long days, but when it arrived the boxes look like it had survived an ordeal. Luckily, the speakers were well packed and came out in great condition. In any event, when shipping internationally, careful packaging, double-boxing and insurance is highly recommended.

I have had excellent experiences with Airborne, DHL and Fedex International. Airborne and DHL will be more cost-effective. Fedex is more expensive but IMO I have found them very reliable.