narkissos,
Seems as though the rendering speed should be better. I don't use Blender, but it- as does most rendering software- can use all available threads for rendering by setting the CPU allocation. From your description, you may not be using all the threads. I have a dual quad core Xeon 3.2GHz workstation with 16GB RAM and a Quadro FX4800, and when there is a large rendering, I assign 11 or 14 of the 16 threads to the rendering so I can devote the entire system to the rendering. A 1920 X 1080 rendering in vray takes about 40 minutes.
Have a look at >
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render
> which describes several techniques to improve Blender rendering speeds.
If you are always running renderings, you might consider having a older Dell Precision with dual Xeons as a dedicated rendering machine- very useful. You can buy a Precision T7500 or similar quite reasonably- (my T5400 was originally $500)- that can sit in the corner all day and night rendering while you work on you main system.
Cheers,
BambiBoom