Warrior Woman, I downloaded Sean's version of Serenity and converted it to an .obj, in a conversion program, I've rendered images of it in Vue, Bryce, trueSpace 5, Strata and yes Poser.
I'll warn you though, the textures will have to be adjusted in each program to look good and that's a lot of work, about 280+ texture maps. This was the Poser, and Corel P-P version.
Firefly
I know it's the Poser version because if you look close, real close, you'll see a little Wash flying it!