I use Fortinet and CheckPoint regularly, I am not a big fan of the Fortinet I have to work with, the CheckPoints are very nice but a little expensive for a small installation. I have tried the free Sophos download in a VM running on a QNAP and seems quite nice, sadly the QNAP really wasn't up to running it effectively.
Am currently thinking the Sophos might be best as on paper it performs well for the money, only thing I am not 100% sure on is the subscription services, need to compare each unit for ongoing running costs.