If you can afford to get the larger wattage, do it. It will last you then an upgrade later down the road. Both makes are nice and reliable, but would question the price range and whether these are the best in it.
am in aussi btw , the seasonic psu is mind blowing but its like 20$ more than by budget . i can get a OCZ stealth 500W but it has only 1 pci-e . I think i have come to the top most picks with these two psu's
if you're willing to jump out the extra $20 i recommend the XFX XXX Edition 650 Watt Power Supply P1650XCAG9, it be easier on upgrading later on down the line, i myself have the 850 and wow does it work