Check the power supply. It says generic 600 watts. Should be enough, but. hd6670 = 63 Watts, gtx560 ti =170 watt stock. = 107 extra watts of all 12v = maybe an extra 10 amps of 12v. If you don't overclock you should be fine. If you OC CPU and Video you could hit problems. This site: http://www.hardocp.com/article/2011/02/01/galaxy_geforce_gtx_560_ti_gc_overclocking_review/
hit 516 watts load when running an OC gtx560 ti with a Core i7 920 overclocked to 3.6GHz (the i5-2700k will draw less the the i7-920).