Well it all depends by what you mean by affordable.

For $199.- subscription fees per year you can get the full-blown Houdini. This is the most pro that a 3D app can get. If you have pro aspirations then this is the way to go. Houdini will open the door to the most prominent production studios in the world (while Carrara will only get you laughed at).

I am only a hobbyist doing occasional 3D for fun, so Houdini is way above my head, but if you consider that 3 years of Houdini subscription will only cost you $600.- then I am sure that you will agree that this is the software deal of the century.