My bad, reading fail. If I need more than one stream at a time, I usually just have another instance of Foobar configured normally without any kernel bypass. That way I can have music and video games at the same time, etc. I don't really need the increased audio quality with multiple streams.
One thing you can consider is installing Foobar twice (I do the portable install and regular install.) That way you can configure each installation differently. For example, one installation could be the new version with WASAPI, and the other the older version with ASIO. If you don't need any of the features of the newer version of Foobar, then I suppose the old version is fine.
Just be careful with flash audio content, have you had any issues with it so far?