I've worked under both MIL STD 2167 and ISO9000 and I can say their both a waste of paper. I haven't looked at TDD but it sounds the same. The best way to ensure high-quality good is to hire excellent programmers. But since you can't always do that, I recommend that you work on the interface design first.

Every piece of software, whether it's a subroutine, module, object, or script, has an interface, either an API or a user interface. Getting it done first gives you a good idea on how to proceed. And once it's done, you can split the work into two: one to write the tests; one to write the code, trying to keep them independent. That way, you have two options on what the interface means and, hopefully, you can catch more bugs that way.