For power supplies, you can’t just go by wattage. You have to actually look up reviews, because some manufacturers use the PEAK wattage figure as the marketed wattage.
As an example, your Enermax may have been able to do 500W peak–which could have just been for a microsecond, but it may not have been able to do less than 380W for an extended period without blowing up.
Also, some manufacturers have PSUs running in very “cool” conditions when testing the PSU designs. And at a lower temperature, all the components will be more stable and last longer. When reaching an actual computer case, however, the temperatures suddenly rise, and now that power supply rated at 500W can only do half of that without overheating and/or dying.
Furthermore, more trusted brands, like Antec, generally use quality OEMs, like Seasonic, Fortron Sparkle, and others, that have higher quality components. Many times in reviews, these higher quality power supplies can actually run GREATER loads than they are rated, and do so while still remaining efficient and do so WITHOUT dying; the power supplies may have even been conservatively rated.
So do NOT take the rating at face value. Instead, do research on how the supply actually performs against the competition, and how it performs in real life. You will be really surprised at how some big 600W power supplies are outperformed by power supplies that are “only” 450W, or so.
Also, I suggest you don’t just ignore power supplies with active PFC, as these may be the better supplies for efficiency, and you may actually want this. PSUs with active PFC prove themselves time and time again as being quite capable for providing stable power output to components, and are often the better PSUs available, anyway, from what I’ve seen.