Yep, Bodystudio is your only option based on how you describe the problem. If your goal is to render an animated Poser scene in Max, then Bodystudio is the tool you need to use. Of course, you CAN export a Poser animation as a range of frames but this merely gives you a separate 3D model for each frame of the animation. To render these 3D "frames" as a seamless animation in Max requires substituting each successive version of the scene for each frame of the animation. I actually did this once using ElectricImage and I imagine someone has a Max script that would handle the substitutions, but clearly, this isn't what you are looking for. 

Another approach, of course, would be to export the MOTION from the Poser animation as a BVH (biovision) file and import the BVH motion into Max to drive the character. I have done this, too, but it requires having a character rigged in Max and also dealing with Max's (character studio) funky implementation of BVH files. I have found the best workflow for this approach is to use MotionBuilder and FBX files. Again, this sounds like something far from what you are interested in and I mention it just to be complete. 

Frankly, Bodystudio is the only game in town and I've been impressed with it over the past week that I've been using it. My only big gripe is that it is not compatible with 64-bit Max, which is a major disadvantage for complex scenes and big renders. However, if you are a 32-bit user I think you'll find Bodystudio is a very useful tool.