i know that is not the limit. i have read of too many people using a xonar card to get 5+ audio channels using a vst host...
though, i never used the xonar card,so can't help much more..
i did post a guide that should be able to get a basic setup of 2+ channels going for you:
but i believe that the xonar supports internal routing, so there are more efficient ways of getting the audio in/out then what i show in that thread..
try searching the high end audio section. i believe there have been a couple of write-up's on using a xonar card..