Seasonic make some of Corsair's units, and the some of the Antec units stand up to the Corsair and SeaSonic units quite well. Higher end, the SeaSonic units are much better, I agree, however for the prices you are getting a hell of a unit that is just as good as your SeaSonic units.
And PC P&C make good units, not great. Their newer units aren't as good as their older ones. They did a Corsair (or rather Corsair did a PC P&C because they did it after) and built up their rep with outstanding units, just to go and cheap out and ride off their earlier success