Specs

I purchased this Dell OptiPlex 7050 via Ebay for around $60.00. It is a small form factor (SFF) desktop, with additional PCIe expansion slots, which made it a suitable alternative to other dedicated hardware these days for firewall appliances. The desktop specs were as follows:
Processor - Intel Core i5-7600T 3.50GHz
8 Gb DDR4 Ram 
500 Gb SSD 
Intel HD Graphics 630
The small form factor version of this desktop came with:
2x VGA ports
Optical Drive
1x USB-C port
4x USB 2.0 ports
2x DisplayPort
1x HDMI port
1x RJ45 ethernet port
The most important reason for selecting the SFF version was its capacity for PCIe expansion. Firewall appliances require 2 RJ45 ports, and these expansion slots allowed me to purchased a Network Interface Card (NIC) and install it on the motherboard. You can find more information about the NIC I purchased on the next page!