from what i read around on forums, i would be alright with a 500W PSU. also, i will be using the PSU to power non of the many fans in the system except for the cpu fan. so it's cpu+gpu+m.board+hdd's
so here i'm shooting for quality and durability. which PSU will serve me better and yes i'm overclocking both the CPU and the GPU.
If you want your PSU to last you should really consider the antec unit.
Lots of people seem to recommend the corsairs and xfxs PSUs these days, but those antec units mostly are solid achievers. They always pick durable parts.