Shade3D reads Poser .PZ3 files, and has Windows and Mac versions. Its "Pro" version price is a bit more more than Carrara Pro. It does support 32 bit/channel color

Unfortunately I don't know anyone that uses it, and there is no Forum for it here on Renderosity, as far as I know (I just looked). ... would be interested in hearing from Carrara users that have tried it.