Hi sg and a warm welcome to the forum.
Take a look at this thread, I wrote quite a bit on electrics and tents.
But to answer your question, regarding what will 3A and 6A run. It varies on the country or more to the point the voltage.
In this country @ 230v:
3A is about 700w
4A is about 920w
5A is about 1150w (or 1.1kw)
6A is about 1380w (or 1.4kw)
I understand France and Switzerland are also 230v, so you can use the above table.
If you look on most electrical items they will list the following information
Voltage 220 to 240 (usually)
then it will give you the amp or watts.
On page 4 of the link Keeley kindly did a long list of watts to amps conversions.
Feel free to ask any question you want on this, it can be confusing
