Danny,

Okay. Altho I firmly the believe the board is next to everything at 10 and less mph and the kite is secondary (btw under 8mph.. you aren't riding anywhere, IMO) here are some of the best light wind C-kites (for our size) I have ridden, in order of best first. (Price has been factored in since that's one of your concerns)

'05 20m RRD Type Zh
'02 16m Fuel
'04 21 m Best Nemisis
'05 17m Fuel

Bottom line, you already reached the correct conclusion (that around 17m will work, tx to Rick) Ask around town there and try to demo a Glide on a light day to see how the board makes a difference
The best compliment a light wind board can get is "it felt like it got windier"
I hear that every time someone rides a glide or aggression after hopping off their board. They HONESTLY think it got windier when they hopped on. Its kinda funny, really, but reinforces the importance of the board in our crappy low wind conditions.

At our size, don't waste your time getting a 25m or something silly like that. You won't benefit at all in low end, and in 12+ you will be wishing you didn't put the thing up in the first place (as Rick said)

(The only reason I chimed in out of my region, is I have experience with light weights... I am light, my girl is even lighter and we have 3 guys here your size )