No, you do not need a 1,000 watt power supply for a system with one 8500GT video card. A 1,000 watt power supply is designed for a seriously overclocked gaming system with multiple video cards. Your power requirements don't even come close to a high end gaming system like that.
The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the 12 volt rail(s) can easily power a system with any single video card made.
Corsair, PC Power & Cooling, and Seasonic are brands with a reputation for high quality. They consistently earn high marks in technical reviews. They are stable, reliable, and come with a 5 year warranty.
The Corsair VX550 would be a good choice:http://www.newegg.com/Product/Product.aspx?Item=N82E16817139004