Get a known brand of power supply that has been around for a long time. Wattage means nothing, really. Amperate makes the difference. Avoid house brands. Sometimes a 450 or 500 watt power supply is a better choice than the higher rated ones... They are all now part of the high profit aftermarket.
All but one power supply manufacturer are now found in one province in China. You have to look at the UL number to know who made the unit. Even some of the famed PC Power and Cooling power supplies are now made for them in China.
There are now many reviews available online, and in such mags as CPU, MaximumPC, and so on.
All power supplies can fail. You want to avoid the cheap brands because they are more likely to emit spurious responses that can instantly destroy a motherboard.