The FreePBX Sangoma 1200 appliance as outlined below and FreePBX Distro. In this configuration the Appliance is recommended for up to 1200 extensions and 300 concurrent calls.

Specifications of the Appliance are as followed;
1U Server
4 PCI Express Slot
6 Onboard GIG Network Ports
Dual 500 GB SSD Raid Drives
i7 Quad Core Processor
16 GB of Memory
Dual Power Supply
Rackmount Rails
1 Year Hardware Warranty
22in D X 17in W X 1.75in H
Box size is 28in L X 20in W X 8in H and weighs 30 lbs