But the HD7850 is not much stronger than 560Ti and my opinion is not worth more money to add to it ...
You should add $ 50 for the 7850 or is it not worth it? I'm not a serious gamer.
If your not a serious gamer then its probably not worth the extra $50. I would look on ebay for a used 560 Ti if I were you, I wouldnt purchase one new as its an old card and you will over pay.