thanks for sharing your experience, i'm sure it will be helpful for a lot of users!
the whole idea of TBS 6980 is exactly to be able to do things like this and i also mentioned about the possibility of using two copies of DVBDream here:
viewtopic.php?f=2&t=39&start=0#p198it should be possible to use this idea with every software that doesn't have native support for dual tuner DVB cards.