Soldato
That count's for very little nowadays. The only guarantee from buying a Seasonic psu is a higher price. Other oem's have caught them up and in many cases overtaken them. If Seasonic are so good then why are they so tight with their warranties?
I got a free-upgrade with Seasonic simply due to hardware incompatibility...
But again, none of my Seasonic PSU has ever failed on me (TOUCH WOOD! ), which is the reason why I would suggest going for AX860.
One minor point to note though, the RM1000X probably is longer than the AX860, so if there's size constraint that should be considered.