Minnowboard Turbot Dual-E (formerly known as SG-2300 series) comes in two flavors:
$249 dual core: https://www.amazon.com/Firewall-Appliance-Gigabit-MinnowBoard-Turbot/dp/B071XNG1BZ
$349 quad core: https://www.amazon.com/Firewall-Appliance-Gigabit-MinnowBoard-Turbot/dp/B0722JRVCH