First Things First
Figure out the maximum number of users you need to support concurrently, and make sure that each piece of the planned systemrouter, ISP, softwarewill support that maximum number. Try to make sure it's set up so that any number of seats can play, not just Jack, Jill, Stan, Mary, and Bob.
Find out as early as possible about product requirements, and then track down the details of what they engender, from hardware to operating system on down. If you're required to use a certain type of hardware, software, or service, you may have to switch Windows versions to use or to best accommodate that product. As an IT manager, you know how often that kind of switch is necessary for specialized productsnot just proprietary vertical products.
As you build outward from the absolutely required pieces, check the requirements of every new building block against the other requirements for all the other building blocks before you commit to anything.
Another item to study before making any buying decisions is VPN security protocols. IP Security Protocol (IPsec) is an open standard that's regarded as more secure than the Microsoft-originated, proprietary Point-to-Point Tunneling Protocol (PPTP). Some products support both, but most don't. IPsec uses standard rather than proprietary encryption, and supports more platforms than PPTP.
For a closer look, see Chapter 3 in MCSE Training Guide (70-216): Microsoft Windows 2000 Network Infrastructure, Second Edition (Que, 2002, ISBN 0789728788), by Dave Bixler et al. You don't have to be studying for an exam for this information to be helpful.
It's important to check out these pre-pre-buying types of research questions about things that can affect your product choices, and then follow up by looking at specific model data sheets online. Do the same with software. Map out what every piece of hardware and software requires and how it interacts with the operating system before you order anything.
With VPNs, sometimes a deep breath, a cup of green tea, and sleeves that roll up easily over flexible elbows can be the best tools you have.