I think it's a BIG mistake to install a firewall and then "just forget it". Especially in a production environment. This is not a static environment. Every firewall release, left unattended, is a WASTING ASSET because it is immediately subject to hostile probing and odds-on to be compromised unless frequently updated to keep up with new attacks. You may be one of the lucky ones to avoid the attention of hackers/crackers, but in a business environment, can you afford to take the risk?
This is one of the reasons "purpose-built equipment is prohibitevely expensive". This is also why, imo, when it comes to security, proprietary, closed products, get my vote, as long as they're accompanied by commensurate warranties on the part of the vendor(s) (It amazes me how few so-called security "professionals" look at the warranties and the support the vendors provide, and discuss in advance what happens if the vendor's system is compromised).
To add to the VPN issue:
MacOSX, before you go splurging on tunnel licenses, estimate the maximum number of
concurrent VPN connections you will need - that's the proper metric. If you need only 1 or 2, there is no need for a site-to-site VPN, since in such case you can establish a (software) client-to-server VPN as needed.
If you need something more robust, easy to use, and proven in the field, the Cisco boxes mentioned above are a good option. Although I think the small-business products by Sonicwall are better suited to smaller offices. But currently, for simplicity and ease-of-use, I'd go with
Sofaware . Their small business offerings are very competitive, and they also sell a home version, which I've been using for the past few months.
The annual subscriptions for security are currently the cheapest among comparative products. The prices for gateway antivirus, antispam and filtering are also right up there.
Ofcourse, security is a very competitive field and vendors keep leapfrogging each other, both in technology and support. Next year, one of the other players may be on top in the small office market. My loyalties are very fickle.