if you wanted to experiment with mods, you would prolly be better off going with the whole tekkit bundle because the mods interact with each other very well and there is just soooooo much stuff you can do.
the downside is that it would also need a full world reset which makes me feel bad for the amount of effort people made creating some of the biggest and craziest minecraft monuments i've ever seen.
they're ez installs for both server and client but i dunno if its warranted just for very little number of players that still play.
at the same time. it might just boost popularity of the server because tekkit is pretty popular right now (the yogscast have a pretty entertaining tekkit series
http://www.youtube.com/playlist?list=PL310728C6AAFF44B1). and rebuilding from scratch is probably half the fun.
up to you guys to decide, i'm happy to have a tw server at all.