120 frames in 3 hours is only 1.5 mins per frame. You're gonna be hard pressed to get renders faster then that in any app at decent quality. About the only ones that can do it are the high end ones like VRay and mentalray (and esp. their realtime/GPU versions) but those will cost a lot of $$ and are not easy to use with poser besides.

It would probably be easier and cheaper to just get a few more machines and setup a farm for your renders (PPro lets you do network rendering IIRC)