7850 is high-end video card instead of 7570 which is low budget card where you will be unable to play games on full HD
6gb vs 8gb doesnt make huge difference since all games run smooth with 4gb ram - tested on my own pc
and about processor i5 or even i7 are worth only in case if you doing some video edit/programming or something where you will run all 4 cores,most games still use only 2 cores - tested on my own pc
So i find pointless buying machine with i7 no matter how rich you are.
900 euro is way too much cash even for gaming config so i would search deeper about better offer in local shops or over internet,600-700 euro would fit anything what you mind to play talking about machine without monitor or installed windows 7.
Check price of this components in NL cause they are best for cash here
Asus P8H67 B3
Intel I5-2500k
ATI Radeon HD 7850 2gb twin frozr
2x4Gb kingston hyperX 1600mhz
Seasonic SS-430GB of better
1TB hard drive
Dvd/rw
and desktop case choose on your own
Should be less than 700 euro.