I have a BCM50 currently with 1 expansion chassis containing a Digital Trunk Interface. I need additional extensions but also 5 analogue extensions (modems/fax's). If I add another expansion chassis (I believe I am limited to 2?) would it be best to add a digital extension interface and then 5 x ATA or an ASM for the analogue extensions and IP Phones instead of the digital extensions? Any advice would be much appreciated.