If you had added a lot of fans in your case, a lot of harddrives, a lot of LEDs and did heavy overclocking then you might want to upgrade the PSU.
Your PSU is awesome, it has gotten a gold award by OCC.
Just to clarify something, just because Seasonic has made the PSU doesn't mean it's as good as a Seasonic PSU. XFX has ofcourse made the design and the single-rail technology that they are so proud about. Not Seasonic. http://www.overclockersclub.com/reviews/xfx_core_edition/11.htm
"The XFX Pro series power supplies are, as you’d expect, physically alike across the range and with good build quality and their unique styling will probably appeal to many enthusiasts. If you are in the market for a high quality wired power supply, at a fair price, then I highly recommend any of the XFX Pro Series Core Edition units. I have no hesitation in awarding all three XFX Pro Series Core Edition power supplies the OCC Gold award."