Fact a computer runs cooler and is less likely to present errors with a good quality power supply.
Fact anything over 850 watts is complete hype with the exception of dual processor server systems or systems with more than two graphics cards.
Fact processors and video cards once again are becomming more energy efficient with the exception of AMD at the time of this posting but AMD is soon to follow. This means less power is required.
Fact gold rated power supplies run cooler than bronze rated and platinum is just a way to charge you more for little differance over gold.
Fact Seasonic has always been a well regarded power supply company amongst all the new brands.
Fact Corsair are likely rebranded slightly modified Seasonics.
Fact Antec made good power supplies then started making worse ones but are now back in the game making pretty decent stuff since Delta Electronics now makes their power supplies.