I would presume that a refurbished psu would be recertified and come with at least a years warranty. I have to admit though that I would never buy a refurbished psu and would be in two minds about using one from a warranty replacement. My paranoid side say's that if it's failed once and been returned and fixed who is to say that it won't fail again?
I wouldn't buy one of those Seasonic Primes though, the prices are very high. If you wanted to try a different brand how about one of the excellent Corsair RMx series? Argueably they are Corsair's finest psu's. Don't be put off just because they are CWT units because they get top marks in reviews. Jonnyguru gave the RM750x
9.8/10 and the RM1000x
10/10.