So to add to @rainer_d comment, I've recently purchased the APU2C4 as my pfsense box and frankly considering the costs I'm rather impressed. I'm have a WAN\LAN setup running Squid, Squid Guard, Suricata, PFBlockerng, and ntopng - my main focus is keeping my kids from getting into too much trouble as they start exploring the internet. Looking at the performance to energy cost, I really feel this box hits a lot of check boxes. Sadly, I'm limited in my bandwidth so I can't speak to how it handles on 1Gbps, but I've hear you can get close but I don't know if would need to limit the packages your running.
If you do end up do end up looking at the APU2 setup, here is what I came up with so far to improve performance:
Get thermal grease and stand the box vertically - Reduced my CPU temp by 10C
Avoid ClamAV, it will eat the CPUs alive with large downloads
Suricata seems to perform better than Snort, but is twice as hard to setup... but twice the trouble is twice the fun in my book. Between the multi core support and the APU2 supported inline mode, you can get IDS on without to much impact to your system.
Get the 4GB version, it's not much more and gives you lots of RAM to play with.