http://www.futuremark.com/news/59213_amd_radeon_hd_6450... < the ddr3 version requires 44 watts and the ddr5 version needs 60 watts. The remaining components in that pc are pretty low powered. CPU is max 95w, the remaining components may pull another 80w max so you will be fine. When installing a dedicated video card its always a good idea to have an exhaust fan to remove the extra heat so things fdont overheat. use this power supply calculator http://extreme.outervision.com/PSUEngine its a good guide to the kind of power you need.