Running out of IP's on a class C subnet

I mange a site with about 80 workstation and a few servers. The only subnet is 192.168.123.0 with 255.255.255.0 mask. We are running out of IP's since we have 30 IP phones and 50 IP Phones + all mobile devices, servers and switches.  I thought of putting wireless on it's own subnet/vlan but I will still run out of IP's on the 123 subnet.  I was just thinking of changing the mask on the the main subnet to 255.255.255.252 .  That way I would also have the 192.168.122.0  IP address on the same network.  We have 3 switches on main floor and one on each other floor. They are Cisco 500 smb switches . I am told if I do this,  it may increase the broadcast packets and slow my network. I thought with all the switches in place and given the size of the network , this should not be an issue.   We have all Windows 7 workstations and 4 Windows 2012 servers.  I can not put the IP phones on another network because they are not cisco and they don't do well on VLANs.

 The alternative is to place a router on the other floors, but I feel like that would complicate things since I would then have to somehow configure the Windows DHCP server to provide IP's to the segments behind the routers and also somehow figure out how to mange the wireless devices with same SSID behind these routers.  Your input is appreciated. Thank you,