To answer your main question, you'll be fine. Only in rare cases would there be an issue, and yet you can say that about most other things in life. I've said this before but I've taken xanax and kava both on the same days with no problems whatsoever. But, and I've discovered this not too long ago, that whenever on a particular day I take xanax say in the beginning of the day and that night I have a kava session...kava's effects aren't nearly as pronounced as how they normally are when taken on a day without any benzo use. I actually never do it anymore primarily because of this. It's a waste of kava for me, but for you it could be different..there's no way of telling. It most likely has to do with the benzo taking action on the same receptors as kava does and afterwards creating a sort of cross tolerance to the kava. I'm sure infraredz can enlighten us with the specifics.
edit: @
Ouroboros, I think there is a fine line between a reference of drugs taken for recreational purposes and ones that are prescribed for illness, especially in concern to their interactions with kava.