hey richo,
You do realize that if you are under cooked with a 14m, a 15 or 16 is not going to make that much of a difference. Why don't you just use a bigger board in the light stuff and stick with the kite you have. Too many guys struggle to get going in the lighter wind because they are on 130's or smaller. Extend the range of your one kite but using an old surf board or a cheap skim board. If i can't get going with my normal board i don't come in and get a bigger kite i will just grab my skimmer for a while and hope it picks up.
I can use my 13 with a skimmer in the same wind as i use a 17 underpowered with a 132..
Just thought you may want to re think trading a kite for one 1-2 meters bigger. I once had a 10 12 16 quiver and sold the 12 and 16 and got a 14 and 18 and i actually perferred the original quiver!
Rich