You need to try on boots and buy what fits your foot. As far as stiff boots to look into: Salomon F4.0, Burton Driver X, K2 Thraxis/UFO, DC Status
I will add my favorite stiff boot, the Nitro Selects
as they have a removable plastic tongue piece so you can adjust the stiffness (without the tongue piece, it is about the same as the Nitro Teams which is their all mountain boot, which I have also owned and liked). I like Nitro because they are the only brand to properly holds down my narrow heels and skinny ankles well.
I used to ride Salomon before that (Dialogue, Synapse, and Malamute), but they used to have an average wide heel and I had to over-tighten them to get them to lock down my heel - this lead to over issues 15-20 days in. I've also tried 32, Vans and DC Shoes, they didn't work for me, but might work for you (although I found 32 boots were not very durable and there liner design are crap in my opinion).
Again... try a lot of boot brands as each fits differently. Also make sure to not over-tighten you boots... you want the laces just snug. If you have to crank down... that is a telltale sign the boots don't fit you well.