I second what hunter said. Corsair is a reputable brand and the tx version of their psu lines have very good longevity. 650w from this baby is more than enough for your configuration, it'll even leave you room for some overclocking.
It probably has another 3-5 years left in its life, it was overbuilt using good components and since you arent running it at full load it has a bit of extra life in it. If you build a whole new rig you might want to replace it with one of the newer more efficient units but i wouldnt bother replacing it until it goes bad or you replace the whole rig.