Firefly can definitely do images like those you linked to, without postwork. It can do better.

Things that make renders better in Firefly:

1. Gamma correction

2. Indirect lighting

3. Good use of direct lights or emitters when needed

4. Good material shaders

5. Subservice scattering

6. Render settings

Unfortunately, optimizing all these things is not a quick and easy skill to learn.

The best way to learn to light a scene is to take a very simple, stripped down scene, perhaps with no textures, and no figures (just primitives), and just play with lighting, doing tons (hundreds and hundreds) of test renders. Because the scene is very basic, it will render very quickly. Because you are adjusting the lights yourself, you will learn what works and can apply the lessons to other scenes.

If you want a quick way to improve your lighting, then IDL Studio 2 at RDNA (for indoor shots), or Sunlight at the same place (for outdoor shots) will help.

But even with the best lighting in the world, if your materials shaders are terrible, you'll still be missing a big part of the equation.

Gamma correction and using Snarlygribbly's Scenefixer script can help with some, scratch that, most of the problems. His EZskin2 will make SSS on skin look divine. Paying attention to the shader threads in this forum and at RDNA can help tremendously with others.

Render settings depend on what's in your scene, how fast your machine is, and how quickly you want to render something.

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Should you use Reality?

There's a learning curve with Reality as well, but I get the impression that it's not as steep as with Firefly. 

But you'll pay for that ease of use with greatly slowed down renders.

I guess you need to make the decision today, while Reality is still on sale. Me, I'd buy it while it was on sale, just because it may be a good tool to have in the toolbox, and the price is good. That said, I have Reality already, but I don't actually use it because I'm too impatient to wait for a render. :)

EDIT: Gack! Reality is not on sale any more. Scratch all that. I'd wait until it was on sale again. :)

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.