It's repeatedly stated in B5 that something happened 100 years prior that led to the Centauri Empire becoming more of a remnant than anything else.
Perhaps it was the Vulcans who blew them back, rather than the Andorians? Might be a nice twist that serves as a "Don't **** with these guys" establishment.
Given how both the Romulans and Centauri have Imperialistic societies, maybe it was a secret alliance between both of them that led the Vulcans to downgrade the Centauri Empire and keep the Romulans away.