Need to change our LAN subnet class. How to properly subnet an 80 person office if you could start fresh?

So the LAN office network I inherited was one giant class A subnet (255.0.0.0) . We have a few VPN tunnels to other sites, and a new VPN tunnel we need, cannot currently be setup yet, due to their side running a 10.x.x.x LAN. I'll list some key info and concerns I have below.

This is an all Windows network. Also all TCP/IP v4.
We have a DHCP pool for workstations and portable devices.
We have about a dozen large networked Ricoh printers, all using static IP's.
We have dozens of servers old & new, all using static IP's.
We have a handful of older Netgear and SMC 1 gigabit switches, using static IP's. No VLAN's going on within the environment.
We have one single gateway assigned to every workstation and server at the moment, a Sonicwall NSA 2400 security/firewall appliance.

While I've setup plenty of small LAN's in my day, this would be the biggest environment that I'm basically going to to "start fresh" and re-do. I am familiar with all the equipment and know how & where to change IP info, subnet info, gateway, etc.

I guess my question really is... what is the best way to subnet this environment out ? I'd like to do whatever possible to keep or improve network performance, reduce / cut network broadcast traffic, and maintain flexibility for adding further subnets in the future. I also do not want to put too heavy of a load on the Sonicwall NSA 2400 firewall; that should really only be getting hit for internet & VPN traffic.

Several small class C subnets ? A larger class B ?

Thanks for all help & advice. Please let me know if you have questions and/or need more details, and I'd be happy to post!