It keeps bugging me - why use name "aria" for passive, while using "bardic inspiration" for active, special boost?
Arias are mostly culminative parts of music works, parts that also "provide the opportunity for vocal display for concert singers" (quote from wikipedia). On the other hand inspiration can be more passive - you can be inspired even by the portrait on a wall.
Please, please switch it around. Is it too late?
Regarding passives linked to warchanter and actives to spellsinger, that is what I always expected from the two trees, so keeps it in theme.
And imho vocal display fits more to spellsinger, Warchanter is more busy with inspiring his or her companions by displays of swordfight (or even axefight).