I bought all the parts and built up my PC on my own.
The desktop was ~700-800 Euros (1,5 years ago) without windows but it is still nearly a High End one.
I never built a desktop on my own, but I really recommend to try it. I saved around 400 Euros by just buing the parts and building it on my own. I don't know if you have good online shops in your countries but in germany we have a really good one with low prices and most important: !!A good support!!
If you think about building an own desktop, the warranty and support is extremely important. So search for a good shop before you buy the parts.
My Pc has a
Intel Core i5 2500 ~180 €
Nvidia GTX 570 ~ 280€
8 GB DDR3 ~ 20 €
1 TB hard drive ~ 90 €
550W power supply ~ 50-60€
Blue Ray device ~30 €
Mainboard ~ 50 € (better buy a more expensive one, it is worth it!)
nice but cheap case by CoolerMaster ~ 60 €
Once again: It is still very good, and it was only 700-800 Euros. I can play Battlefield 3 in Ultra-grafics at about 30FPS (on a 1920x1080 screen). GW2 runs at around 50 FPS at highest grafics.
I really recommend to wait one more year for the new chip generation. My Pc parts are still ranked in the High class and not much worse than the new generations. I would wait to get the '14 grafics card generation and the '14 processor generation