I'm sure the amount of tuners on 1 box have nothing to do with it, it's your IP address connected to the server, if a server only allows 1 device from your IP address then that line can only be used on 1 box at a time, if the supplier allows more then 1 device to be connected to the server from your IP address then the same line can be used on 2 boxes or more if allowed. To summarise 2 tuners don't count as 2 devices it's the amount of separate boxes on the same ip connected to the suppliers server, any good supplier would tell you this if he/she says otherwise and sells you separate lines based on the amount of tuners on 1 device then your being scammed, for the record I've never had any issues using 1 line on a twin tuner and my other single tuner because my suppliers at the time allowed it.