To the OP:
Go march Spirit. Knowing several of their brass staff personally, I can guarantee you will get a wonderful experience there.
Besides, at 16, you're not going to make Crown or Cavaliers anyway.
Ok, now this is way to generalized and overstated. Again, as I said in my previous post. It's not unheard of to have kids at that age in corps like Crown and Cavies. Rare? Yes. But it does happen (I really hope someone can come in hear and confirm my fairly certain info that Crown marched a 14 year old recently). For you to say point blank that someone "won't make it" is hyperbolic and unfounded.