OK, what is the difference between 256-bit and 128-bit graphic cards?
And what do you think is better when 5670 and 9600gt is compared?
All other things being equal, a 256 bit card is better than a 128 bit card, it has more bandwidth for the memory (the "pipe" size than data flows on).
As far as comparing 2 video cards, look here http://www.videocardbenchmark.net/gpu_list.php,
put in the models you want to find, you'll get a speed test result and a rank based on the other cards in the chart.