well, its a bit difficult b/c that site is not all english, and i use newegg for 99.999% of all my computer needs, but i think this is a decent build...
btw, i would NOT
buy that comp that is premade for you... build it urself, ull save money and get a better overall system by FAR.
+119 compustar - the star in hard - and software
seems like a good mobo to me. Didnt see all of the ones im used to thru newegg, but thats b/c it looks like you are in another country... however i did recognize this one, and i think most people are satisfied with it. you might wanna google it to see how well it overclocks with the Q6600, as i am not sure.
+85 compustar - the star in hard - and software
+220 Q6600 for the CPU you said... good choice... but i am not sure if this is G0 or B3.... you may want to investigate this before buying.
+99 compustar - the star in hard - and software
+250 if u get the 8800gt
+230 if u get the HD3870
for the GPU, a great way to save money would be to go with the 256MB version. It works just as well but it wont be able to support the higher resolutions. i think you will be fine with this card, and you'll save a good deal of money, about 80€. I didnt see any on your website, so you need to find another comp site for your area.
both of them are great GPUs, you'll love either one of them.
I didnt include a PSU b/c i didnt like any on that website, but i am no PSU expert, they might be fine... i just wouldnt trust me to pick any of those out, hopefully some1 else will be able to guide you towards one of these.
+80€ for psu (estimate)
this puts you at 820€ if you get an 8800GT.
the best way to shave money off and not lose much performance would be to go witha lower size HD. I am not sure what you will be using this comp for, but generally 250gigs will work for now and you'll always be able to buy another HD down the road. doing this will save you about 45€.
if you go w/ the 256MB version of the card which i couldnt find on your website, it will save you about 80€ more.
this puts your total to 695€.
not sure what your current PSU is, if you can reuse that one then you'll be back undrebudget and you could afford a 320gig HD.
i know this build has many options to it, but i hope it helps.