Well, newegg.com has a "power supply calculator". Go to "power supplies" in newegg and then there should be a little box in the middle of the left hand side that says " what power supply do I need?" Click on it and it should show you. 1000w is almost WAY overkill for any system.
You have to look at the calculator and the recommend PSU requirements from your Graphics Card to truly come up with your requirements. You can run with the lower wattage, but I wouldn't recommend less than what the GPU calls for... IMO.