I was with you right til Call of Cthulhu, SQ. Call's my all-time favorite game to run. Just point out that there's a lot of Lovecraft in B5. You could call it a crossover and just use more First One plotlines. Anything the First Ones tend to do would fall easily into Lovecraft's mythos. Though really, it's hard not to run Call if you have the players for it...
And as to the "B5 Geekess" thing, I had just the opposite thing happen. *I* was feeling like a total geek fanboy, but my players are, if anything, more into B5 than I am sometimes. Which I thought was impossible. So I'm lucky. Here's hoping I can keep them interested over the long run.