Hi 3DVim

What you have to consider is your pipeline,  the projects it will produce,  and what aspect will be your backbone.  From my experience here is the basic pipeline:
1)    3d Modeler
2)    UVMapper
3)    Image Editor
4)    Renderer

If your goal is to create the mesh for the landscapes then the 3d modeler is your backbone.  If you intend on utilizing existing meshes then your backbone is the renderer.

My current pipeline consists of:    Lightwave,  Silo (3d modelers);    Lightwave,  Silo,  and UVMapper Pro (UVmappers);  Corel paint essential, Paint shop pro, Photoshop Cs2 (Image Editors);  Daz Studio,  Lightwave,  Poser6,  Vue 5 Infinite (Renders). 

As you can see one program alone fills 3 of the billets. 

Side Note:    When creating content for Poser, UVmapper Pro is a must.  It can fix a mirade of problems associated with the Wavefront format.  ( Please o Please let Poser7 use the FBX format instead of Wavefront!  Also an online render farm would be nice too!)

One last piece of advice don't be in a hurry to buy.  Try out the demos,  and grab some freebies.

Cheers!

patorak