The Chieftec BPS-850C2 and the Corsair GS800 are similar from a technical standpoint and do not differ much in price. The Chieftec can offer semi-modular design, somewhat higher output power and better efficiency whereas the Corsair has an original exterior, highlighting and lower voltage ripple. Both are quiet at medium loads (especially the Corsair), but become noisy at high loads (again, especially the Corsair).
The Cooler Master Silent Pro M2 850W is much quieter than the mentioned pair at high loads while its electrical parameters are overall better. However, it costs considerably more while its cable system isn’t optimal (we mean the connectors for graphics cards in the first place).
The Seasonic SS-860XP is a real technical masterpiece, but costs almost twice as much as the Cooler Master Silent Pro M2 850W. We wouldn’t say that it is twice as good in terms of consumer properties. On the other hand, we have no doubt this PSU will find its customer even at its current price.