Just as a point of comparison, if you're curious about non-Fortinet options, Palo Alto just announced the PA-445 which includes an SFP cage. If you're on a budget then just stick with Fortinet, but ...

Fortinet's FortiGate 5020 is built using a powerful chassis containing dual, hot-swappable power supplies as standard, building in redundancy. The chassis can also house two 5001 blades, each of which ...