Sophos is free for home use ... Either via Sophos Home or with the Home UTM which gives you endpoint licenses for 10 machines.
Details of the HW for my UTM:
Status: Working, currently using at Home
Astaro Version(s) tested: 9.355-1
System OR Motherboard: SuperMicro E200-9B containing X11SBA-LN4F Mainboard
BIOS version: 1.0
CPU: Intel® Pentium® Processor N3700 (SOC), Quad-Core (6W, 4C); Socket FCBGA 1170
RAM: 2 x Kingston KVR16LS11/4 RAM 4 GB 1600 MHz DDR3L Non-ECC CL11 SODIMM 1.35 V, 204-Pin Memory Module
Disk Controller 1: SATA 3.0 (6Gbps) from Intel® SoC
Network Interfaces: Quad Gigabit Ethernet LAN ports, Intel® I210-AT
Video Controller: Aspeed AST2400 BMC
Hard Disk: Plextor PX-128M6M 128GB mSata Solid State Drive
Case/Chassis: CSE-101S Mini-ITX (19.5cm wide x 19.5cm deep x 4.5cm high)
Power Supply: DC-DC board with external 60W DC Power Supply
Total Power Consumption: Estimated 10 - 15 Watts
Total Cost: £424.63 (Bare E200-9B = £350, RAM = £29.24, mSATA = £45.39 all retail)
Comments / Notes: This Server/Board has a dedicated IPMI interface (similar to HP ILO) in addition to the 4 NICs.
Install of UTM was done remotely using IPMI console redirection with virtual media pointing to local ISO on remote machine.
All hardware was recognised with no issues.
I did splash out on a Sophos AP which allows me to do multiple VLANs , captive portals etc from the UTM.
A couple of links:
Free Antivirus for Home Networks: Secure 10 PCs and Macs Free | Sophos
Free Firewall for Home Users | Free Home Security Appliance Download | Sophos XG Firewall
Free Home Edition Firewall - UTM Home | Sophos Free Tools
Have a play, both the UTM and XG Firewall can be stood up as a VM if you so wish.