Get a different graphics card. Quadro K600 is low-end.
 

I would recommend looking at the hardware requirements for the software that you will be using and figure out the "worst case scenario" Work your way backwards from there to determine what you need. Your computer should not have any bottlenecks. This means that your CPU, GPU, and RAM need to "balanced". 

This is how I look at it: rendering is CPU heavy, modelling is GPU heavy, and both processes use their fair share of RAM. This is where you should invest your money. If you can afford it, I would also recommend a SSD for you OS and software. They have come down in price quite a bit recently.

All the other equipment is secondary (monitor, speakers, keyboard, mouse, etc.)

Here's a helpful site for picking out parts: http://pcpartpicker.com/

DO NOT waste your money on the Quadro. Get a Geforce or AMD Radeon card, they work just fine. However you really need a core i7 processor and at least 16GB of Ram.

My 2 cents

http://www.boxxtech.com

I work IT for starchitects, and this has been my observation:

Any workstation class GPU (K600 and up) is fine unless you're planning on using GPU rendering programs such as Octane.  Otherwise, like ark1t3kt said, most rendering software will rely only on the CPU.

To that end, I would recommend the highest end Xeon you can afford, as much RAM (16GB min) as you can afford, and any current GPU (workstation grade or not) should be able to run all of your modeling needs.  I would not recommend Leadtek--I've had bad previous experience with their quality of product.

If you're using something like Octane, then get at least a GeForce 580 level card, and spend money on a multiple (i.e. SLI or Crossfire) card setup.  They work best when scaled. Get any quad-core processor to meet your other computing needs.  RAM recommendation stays the same.

BOXX rigs are good examples.

Thunderclap -

Side question: Is Octane a popular renderer among higher-end firms? What kind of rendering software is preferred in so called "starchitect" firms? I always imagined that Maya, Max, Rhino Vray etc are still the go-to renderers.

@Roshi

I read the interview of one of the partners of this firm www.luxigon.fr and 

he said 80% of the works are done on Photoshop !

Siamese Dream, Photoshop is not a rendering software, it's primarily used to touch-up/embelish renderings which are produced from others. The images on the site you link look close to what I can crank out using Rhino and Vray.

Perhaps the interview suggested than most of their work is using photoshop to touch up renderings, I can see that being a thing because it is often easier to fix a bad render than wait 8hrs (or more) for a new one to generate.

Non Sequitur ,
Rhino and Vray is 20 % ... that was what i think he (the partner)meant from the article.
What i'm trying to say is, Photoshop is ( thier) magic wand. It's faster and easier to control.

Btw , i used Rhino and Vray extensively in the past 6-7 yrs.

Siamese, point taken, it was not clear from your original post what you intended. I tend to be the go-to guy in my office for any photoshop work... which is fine although it's not the best use of my time when the licensed architect needs to fix the tech's renderings. At least I can control the final image, which is important.

I miss Rhino, it is not very common in my sketch-up saturated market. At least I convinced my office to purchase some Vray licenses so that I can still output decent renderings when needed.

Hello!!

Try to get a i7 core and a NVIDIA Geforce, at least GT 740. With 1000USD you should be able to do that!! Check the msi brand.

thanks so much guys. really helpful! Your all top people.

If anyone has any further recommendations feel free to post them!!