If you are going to build it yourself I will recommend looking at the configurations at Komplett and then shopping around in the Norwegian netshops for the right parts. Have your focus on the processor, amount of RAM and graphics. You will always be able to upgrade at a later point if your demands grow or the new games demand too much. Besides looking at Komplett. Try Proshop.no
I have used them several times and if you keep an eye at their sites you will be able to find som nice offers from time to time. I have been pretty happy about Proshop's customer support when asking for help about my choises.