I'd like to think that I'm not that egocentric Fred. Maybe something like Stahlite or other would do. I'm basically sounding the idea to see if people would like having something like this to flesh out the background of the setting a bit.
Also, I believe you're overthinking it Osaka. The aim isn't to create the best material possible, but one to fit into a certain niche or gap in the setting to further flesh it out. Steel has always had a certain affinity for carbon, so it can easily be explained IC that the material copes far better with the inclusion of carbon nanotubes and the like than the aluminum based Durandium. That way, we can say that inch-per-inch, it's a bit stronger than Durandium, but also that much heavier in proportion to how much better its various properties are. Though it can be used for armor, what I had in mind was that this material would usually be included in building construction because it was cheaper but heavier in comparison to Durandium. Cheap is nice, but for use on a power armor, it's weight is simply less desirable, especially since the non-stainless versions are the most protective ones, and will rust.
It also opens up some more avenues for increased depth with fodder or low-end power armors we may face; having a faint bit of rust dusting its exterior or running down its contours where water has flowed has its own distinct visual flavor.