I used a PCPnC 1000W in school to run my QX9770 and HD4870Xfire, it worked so well I bought myself a 750W unit and have had it in at least 5 different computers. In order of reliability:
Seasonic/XFX - God tier
PCPnC/Antec/Old corsair - Awesome
Everything else especially coolermaster - Dont buy them
PCP&C Turbo-Cool 550, I think, set a new standard for that industry. If it didn't, it was "top-shelf" some years back.
Eventually, they were selling a line of "Silencers." All of the Silencers were rebadged Seasonics.
I wish I'd saved the link, but someone did an analysis of PSU's by brand, tracing their actual manufacture to the source. Seasonic was one of two -- at most three makers -- who had no rebranded units in their product lines -- which were exclusively of their own manufacture.
A lot of XFX units are actually rebranded Seasonics.
I think it could be an oversimplifying choice to stick with one manufacture of PSU without periodically rechecking reviews and ratings. But I've used Seasonic exclusively since 2007. They all had 5-year warranties, and if any appeared to be going south, it was after the sixth year. That particular unit had been abused: it was allowed to remain in sleep state for days at a time without hibernation.
One exception: I purchased a Rosewill Fortress 650 last fall and installed it in a family-member's workstation. It was a "Platinum" model with a 7-year warranty.