As far as I'm concerned, its easier to learn windsurfing than kiting.
It really depends what you want and whether you travel and/or compete.
A few years ago in Tarifa there was a group who seemed to kite (one board, one kite) up to about 20 knots.
Above that, they seemd to be on a 5.0 or smaller and a wave board ( or something small anyway!).
In reality, we all have too much equipment.
Travelling with kiting kit is a breeze.
Whatever, enjoy yourselves and dont get so beaten up on what kit you have !