nice work greg. i have 8 or so years of music making under my belt, including lots of time studying music theory.
C is without a doubt the most common note/chord in all of western music, it resonates with us humans very well. I think all the notes (A-G) resonate particularly well with us, at least on a musical scale of tones. i have found through personal experience (writing a song in F#) that F# resonates very well among the traditional A-G. i've heard tom morello (rage against the machine) refer to F# as "the rock note". for further example, and some poops and giggles: i wrote a song in F# (actually starts in F#, in the bridge it's all about C, and ends on F) which was eventually called "dead world". you can hear it here:
www.thistimeitswar.com
i'm not sure why you wouldn't be finding a harmony system outside of 440, i'd image you'd find them in the same pattern. but then again there's probably a reason we're centered around 440, you may have to work with microtones (tones between the traditional 'semitone'/between F and F#, D and D# etc.)
you'll probably want to take a look at the circle of fifths, if you haven't already. it's a great tool to seeing all the math, geometry and patterns in music.