I like this Seasonic PSU because, IF I win, It would be used to run my 3x crossfire and prove to me that there is a psu that could replace my expensive Enermax psu. Also a brand that I could recomend to others other than expensive Enermax for reliability and function in their systems built by me or not.
Because Seasonic is Californian, mainly. Also, when tier-1 parts companies buy YOUR goodies and put THEIR badges on them, that's a hallmark of quality.
My X-560w has been powered numerous rigs including an i7 and GTX 580 with zero issues and is dead silent. I also absolutely love the semi fanless design some of the PSUs have!