The only two units I know can be networked are the 788CI HD's. The only way to network the 798CI SI and the 788CI is using interlink. I bought a used interlink and I cannot get it to work (I think it's a bad unit). So the only way I can use an external link is to buy three. One for 798, one for 788, and one for the two 788CI HD's. Am I understanding that correctly?