I've just bought a zgemma s2 enigma based plus twin tuner. You would have to use an extrenal hd rather than the internal sata drive you can use for the 800hd. Sub £70 from China and £80 from uk. Openatv officially support the box.
Im looking at the gigablue hd quad, with dual cable and dual sat, i was thinking of the duo2 but gigablue has one extra sat tuner, i also here the gigablue is a bit faster