Range extender or hard wire sensors

They do not have a range extender.  If you have the SS3 system, it is supposed to have a much greater range than the SS2 system.

You can modify SS entry sensors to hook wired switches to.  Of course, it voids the warranty on that sensor.

How large is the office building and what are the interior walls made of?  Got any attic space that doesn't get too terrible hot?  Our building for example has an 8" tall insulated ceiling with a floor used as storage space.  If we were to use SS at the office I could put the base up there where it has less walls to travel through to reach sensors.  You'd lose the announcements from the base, but I would imagine in an office environment that wouldn't be a big deal.