The FreePBX Sangoma 400 Dual Power Supply appliance as outlined below and FreePBX Distro. In this configuration the Appliance is recommended for up to 400 extensions and 150 concurrent calls.

Specifications of the Appliance are as followed;
1U Server
4 PCI Express Slot
6 Onboard GIG Network Ports
Dual 250 GB SSD Raid Drives
i5 Quad Core Processor
8 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 21 lbs