Regardless of what fanboys say, the charts tell the real story.
Your PSU should be fine with a GTX 470. GTX 470 power consumption with a OC'd Core i7 920
The GTX 470 is showing some good numbers for DX11 which is a good sign when you're thinking about future games.
To me it looked like the GTX 470 edged out the 5850 when AA/AF, SSAO & Tessellation quality settings were turned up.
Thats a good thing for gamers who like the 'eye-candy' settings.