I suggest that you get/borrow a copy of George Morris's "Hunter Seat Equitation."
You are talking about hunter heights, not jumping heights. You do not need a 17+hh horse to get over these sized jumps. The author was a multiple USET team member and coached several USET teams. He is now in his 70's, still rides/trains. His advice can help you to buy a horse that has the correct conformation for jumping and to match the horse's build to your own.
This seems insignifigant, but if you find that you buy a talented horse right from the start, you'll be disappointed if the size doesn't match YOU.
My DH dearly loved his horse, "Tyke", (1970-1998, RIP),but Tyke was too small for him.
Tyke was 15'2hh
His current horse, (16'3hh) matches his 6'5" height much better.
So did "Trogdor",(16'2hh) (1984-2008, RIP)
Me, on "Dandy Silver Moon,", 1987.
HE would have made a good hunter prospect, BTW.
Notice how my friend, on "Toma," is undermounted, she is too tall for him.