After testing, probably adding Subdivision from within Poser won't solve the problem. Depending on how high poly your original objects are to begin with. Going by the images you provided, they're pretty low poly so subdivision in Poser will too radically change the object shapes. You could always mark relevant edges as sharp or hard in your modeling software and add a level of subdivision there,  maintaining the shape, before bringing into Poser. 

I would say that bwldrd's solution of turning off smoothing would be useful for Firefly but has no bearing on Superfly rendering. Same with crease angle. Render smoothing is strictly a Firefly thing. With organic models it's easier to get around this with adding a subdivision level. Low poly hard edge models need a different approach.

If you can't or don't want to manually add loops to smooth out your bevels, you'll need to utilize subdivision externally and manually set what edges you want to retain sharp so that it propagates to your export; apply modifier/smooth group in Blender obj export or baking in hard edges/subdivision in Wings for instance...