A couple of additional things to consider. First,
I would be concerned with "pots" compatibility.
Plain old telephones will be plugged into a system,
like it or not. You should know that Vodavi,
for example (not the only one), requires an analog
adaptor to plug in a Pots. Who cares? Well,
if the customer wants a cordless system phone,
and don't want to buy one of the manufacturers
proprietary models, they'll want Pots compatibility.
Remote programming capability is very desirable,
as is the ability to backup and restore programming.
A plain old Panasonic am/fm radio with power cord
and earphone jack set to an innocuos radio station
costs less then $30 at retail, and will provide
fine background music. Any brand of radio will
do....
Distinctive ringing? You may want to know the
difference between doors, for example...
Who knows what CEDIA will bring? Let's check
back after the event and regroup.