Hmmm...
This is a tough one.
PayPal requires that you ship to a confirmed address to take advantage of their sellers protection. Here are a couple of links to PayPay security:
Link #1
Link #2
You can ship to a non-confirmed address but now you are at your own risk and not subject to any protection services that PayPal offers.
Technically, this person could pay you through PayPal, receive the Dual then claim he never received Dual and file a claim with PayPal for a refund. He gets a free amp and you are screwed.
Your auction does state that you ship Worldwide.
This is what I would do...
I would tell the seller that per PayPal rules and given the amount of the sale (i.e. $2200US), you will only ship to a confirmed address. Since the address on his PayPal/CreditCard account is in France and not in NH, you will wait for him to get back to France and then mail the Dual to him at that time.
Remind him that he will be responsible for all shipping charges and any taxes/tariffs due at customs for the amp. Also tell him that you will not lie on the customs form meaning that you will put the entire value of the amp on the form. Usually when people from overseas buy things from the US, they will ask you to claim a lesser amount so the taxes/tariffs will be lower. This is a bad idea because should the amp get damaged/stolen, you can only claim what is on the form.
Good luck and hope this all works out for you.
zeeman
PS: By the time I finished my reply, sundaypunch already replied regarding shipping to a confirmed address.