depends on the cpu, motherboard, how many hdds, fans your case contains.
if your pairing it with say an amd 8350 you will need 120w for the cpu, 20w for the motherboard 10w per fan, 20w per hdd, 40w dvdrw and then add in about 140w for the gpu.
you will likely be very close to the max output of that psu, certainly over 80% usage which will shorten its life quickly if its not a very good 1.
so for the sake of saftey i would say get something a little stronger for the psu to give you some headroom for other parts as well as the gpu.