Well here is what I think. (I will disagree with Zonkerman on a number of things) Value well Blender is free but a bit of a challenge. Lightwave is cheap for you and so is XSI a lot of people are switching over to XSI because of the features and price. I think  for just modeling Wings is the best value out there free and good there are some top pros who use it.
   

     When you get your software get to knwo the tools and what they are. I use wings a lto but I go thru Maya tutorials and I can because I know my toolset. Once you know yoru toolset you can do tutorials for other software and learn techniques. Pricipals remain the same in modelings and often in rendering. Tool location and names often change etc. I like using what I use because wings is a limited toolset and it is very easy to navigate.

     Rendering is a product of just CPU and ram as far as final renders go. But modeing renders aka  your workspace is done by your graphics card. So if you are modeling and you have a weak graphics card you will have problems getting high res meshes and being able to do see your work.

   Rendering quality is due to a number of things. Some programs lack options that advanced renderers have. Advanced rendering options are soft shadows. (most programs will support that now but a few still don't )  HDRI (High Dynamic Ranged Imaging) image based lighting. GI Global illumination the ability to have light comming from everywhere. SSS (Sub surface Scattering) this is making objects translucent makes for better skin and you can make soem things like Jade. Fresel shaders shaders that change color depending on angle. Rendering quality also has to do with the quality of aliasing and just how the code underneath was  written.

My advice download wings and MOI. Both are free and not crippeled demos so if you like them you can continue using them and add them to your toolbox. If you like wings then Silo might be a decent step up. If you like MOI then Rhino would be a step up. Carrera is a good tool for renders and you can put it to good use for now. Once you know the toolset then you might know better what is lacking and look at other programs.

The wit of a misplaced ex-patriot.
I cheated on my metaphysics exam by looking into the soul of the person next to me.