6000+15500=21500ctc

MY current pc i5 3450 asrock z77 extreme4 sapphire 7850 gskill ripjaws x 8gb corsair force gt 120gb wd caviar green 2tb corsir gs 600 ok so now i want to upgrade my pc....i was thinking of crossfiring 7850 but i have gs600..some say it can handle some say it cant some say better be...