Had to take a few moments to remind myself what the Storm Warden scheme is (
http://wh40k.lexicanum.com/wiki/Storm_Wardens)
Sounds to me like your suggested colours might be coming up a little dark - I'd be aiming somewhere around Calgar Blue for the final edge highlight. Don't forget, you've also got the white greaves, gloves and knees (I know lots of Storm Warden pictures show them in silver, but the ones in my Deathwatch source books shows them white, which I prefer). I'd suggest starting at Administratum Grey, then layering up all the way to Space Wolves Grey, with extreme edge highlights only in Ceramite White. Some translation to the newest colours may be needed...
Do you have any pictures you could show us?