More then enough, just make sure it is a different PSU then the Aspire 500watt... mine blew up and didn't AUTO SHUTOFF like it should have, thus killing my neo4 plat SLi board, my Ballistix RAM, and one of my 6800GTs!! Asswiping Aspire.
Yes aspire power supplys leave much to be desired,if you are looking for a reasonable but powerful power supply try the xclio line of power supplys i had a 480watt it was very quiet and stable
500w is ample power.
Thing is don't just buy a cheapo nasty power supply just because of the hefty wattage, Make sure it's good quality or you're wasting you're time.
Hope this helps a little