You didn't mention which model of Thor boots you're using currently, but if they are some of the lesser expensive ones, they sure wont provide as much protection as a higher end boot will. Unfortunately, you'll need to spend some $$ to protect your feet, ankles and lower legs, there's no getting around it.
Once you do get into a better boot, it's take a little time to get used to them, all that protection makes a boot feet a lot stiffer. Don't give up though, soon enough you'll forget you're wearing them.
Which brand? If there's a shop close by, by all means go down there and try on as many as you can. Different brands fit different feet better than others. As long as you stay away from the bargain version that most companies offer, you'll be doing okay. You don't need to buy the top of the line, most offer a less expensive model that offers a great deal of protection.
Good luck!