Great choice welcome to 3D, It really doesnt matter what software you use as long as you get the results you want. As far as Poser or Bryce are concerned they both are 3D software packages (you can import and export geometry) - just not modelers in the sence of a more dedicated packages. The first program I used to get in tune with 3D was bryce then raydream, bryce has a great manual expaining a lot of 3D jargon I later moved over to raydream because I wanted to make objects to render in bryce and soon added poser to the mix to do the same. I recently upgrade to Carrara 4 Pro mostly for amapi designer (much better interface then the previous version) I think you will find the landscape tools easy to use and intuitive the the sky's can be made to look very nice with little effort. Happy rendering