Doug,
A long time ETS follower here.
After read your post, I sniff on the data transmitted between your server and my PC a bit. What I find that forum "forums.equipped.org" is using the Apache server. Though most likely I can fingerprint the underlay OS from here, but to avoid causing any alarm on the hosting company's IDS as a hacker, I use the information provided by "netcraft.com": The server OS is Linux.
Apparently the forum is using UBB BBS software. According to
http://www.ubbcentral.com the basic requirement are PHP 4.3+ and MySQL 4 or 5 ,these two software packages are standard components provided by most hosting companies these days, especially those offer Linux server hosting.
Though the existing server probably is a high-end dedicated server using mirror hard disks that makes it still running even one hard disk already dead. But based on the 3GB data and the concurrent users shown by UBB software, I would said that other IT Pro in here would agree that, with the available server power now, ETS does not need a dedicated server, rent hosting space. from hosting company is enough. Which is much cost effective.
To simply the transit, keep using the UBB software is the best solution, unless some drawbacks on this software has already been noticed. If the current system administrator really have no time for the last help, and none from here can stand up to take up the task of server migration. It looks that UBB authors charge $150 to do the job, so the one time investment probably are the $150 + $139 for another license (probably???), then here is the annual hosting fee which probably $300 - $400 for a year. Now we have two votes to pair.com, so it is a good candidate.
Rising hosting money each year can be considered, the members who contributed can be put into a special member class, such as: honor member. I think a few IT Pro could step in as part of the system administrator group to assist at least the transit period and planing.
email service is bundled with most hosting plans, or it also can be moved to such as paid google mail service for the better spam filtering.