As a general primer on selecting a kite, I always say get the perfect kite first. Ie. get the kite that you will be using more than any other. So, if the right kite is a 9, then do not get the 10 + 8 combo. Rather get the 9, and then fill up around it. Obviously this is just my opinion, but my strategy I think keeps me in the water happy most days because I generally have the "right" kite.
I'm your weight, and I also like being powered more than underpowered.
For instance here, I'd say more than any other kite I use the 10 Park. It is pretty much always in my car when I go kiting. I'd say the windspeed is usually around 20 mph. It is a little hard to say since the wind is very funky at my spot.
Now what is the average windspeed on the most days that you ride? I think you can go at 17 mph fine on the 10, but if the wind is averaging 15 knots / 17 mph most days, I'd say get the 11. Actually if the wind is 17 mph on average, go with the 12.
However the way I read your post is that it starts at 17 mph...what is the average. If it is about 20 I'd say go with the 10. For lower probably the 11 (I have not tried that kite). For the 10, I've ridden in in a session where the wind was from 5 mph to 30 mph. No problem..well I am not claiming I was riding upwind in 5 mph, but the kite flies fine in really weird wind. I think they improved the gust handling this time. It is my all time favorite kite. Handles gusts easily but still turns fast for riding waves and jumps really well.
Now for the high end, I think the 8 could handle 35 knots, but you'd be lit up. The new kite handles gusts better, but if the wind is really squirly the bolt does handle unstable winds better. Either kite floats down the line fine, Bolt is not as fast turning as the Park but in the smaller sizes it is plenty fast for wave riding. It is also a little more grunty than the Park. Both kites are awesome, but I like the Park better. Personal preference I guess.
So I guess what I am saying is that is the wind is very gusty then Bolt is a good option, even if the gust handling on the Park has improved a lot.
In terms of size. If the wind is solid 35 knots, I'd say the 7, but if it only reach 35 every now and then the 8 might be an option.
Would your dealer cut you a better deal if you were looking at a 11 - 9 - 7 set? It really depends on how many times a year the wind reaches those conditions.
Oh and both kites relaunch easy, and for super fast relaunch you can attach the light wind relaunch system...the kite will pop up super fast.
Ugh, sorry for the long reply. This topic is something I obsess over.
What spot are you at? Does anyone ever kite at Bergen aan Zee?