It is interesting that they didn't put visible impulse engines on the Steamrunner-class for the DS9 episodes, as it was mostly a new rebuild of the model. Much like they had to do for the Saber-class.

Incidently it's pretty difficult to tell if the Saber had the usual impulse engine glow in First Contact either, something that was corrected by the time the version which appeared in DS9 arrived: Saber CGI reference and Saber onscreen.