I've got Sky SD with the suitable blue access card, but want a better STB with HDMI without paying for MySky. It would be nice to also play AVIs. What should I look for in an STB to know if it will work with Sky? I'm specifically considering http://airbox.tv/media/djcatalog/Airbox%20S505.pdf which is a clone/rebranded/OEM of Medi@Link Black Panther. I will likely look further so keen to know what are the specs to look for. Thanks.