If you don't mind Madison going to always be mistaken for a girl.. Being named a "girls" name for a boy takes a toll on boys, much more so than gender neutral names, or girls with boys names. For that reason, I wouldn't use it (and I am a super feminist, but my kids psychological well being is more important, I think).. Anyway, I think Spencer Madison would be a great name.. you can do anything with a middle name :)
And I LOVE Octavia.. love, love, love it!