I REALLY needed this post. I have been using power supply calculators to work out how much my new build would require, and always thought it was off. Looking around everyone seems to say "You need at least 500W PSU to run XYZ", now it seems the calculator is correct. I will probably look into downgrading my PSU in that case, maybe going for a 400W one. I cannot see the point of going SLI/XFIRE, nor quad core. I also never cared for the high-speed hard drives. I am happy with a 7200RPM one.
I have a question though, Is there a chart rating the quality of different companies? I have seen some REALLY cheap PSUs (example, Sansun 450W for 24.99, or Ebuyer Value 550W for £21.99) . I am a big fan of reliablity over performance.
Again, thanks for this post.