I think the best thing you can invest for the moment is some time!. Take a look in the applications sticky at the top of the forum for some information on free applications, then try some out. From items like carrera / truespace through to the top end pro-applications you will find that they can all model and export .obj files that will go into poser (you may find with some of the apps you end up wanting to take up the figures from poser to your new app).

The most important thing is to find what suits you. I love 3ds Max, I quite like cinema but get frustrated with it's material handling, I dislike maya's interface, etc etc, but this really is personal preference from use.

I would really suggest trying out what you can get for free first! so either learning editions/demos of the big apps or try k3d (one of my favourites for free ware) / blender / wings and see what suits. As you get a little more experience you'll start to work out your own work techniques and can then make a more informed decision on what to buy!

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Toolset: Blender, GIMP, Indigo Render, LuxRender, TopMod, Knotplot, Ivy Gen, Plant Studio.