The problem isnt just how many watts your PSU has and what devices you are using. Most MBs are not capable of running anywhere near the maximum number of USB devices as the bus was intended. You really need to put all devices onto a powered USB hub. There will be "experts" tell you that they get away with doing this or that... dont listen. The price will be a blown USB bus MB and possibly PSU.
Depending on the type of PSU and what its actual rating is Gold/Silver/Bronze tells you how efficient the PSU is. Efficiency tells you how much energy is lost to heat during use (basically). So if a PSU is rated at 60% then 40% is lost to heat. PSUs are tested for their efficiency at 20% 50% and 100% load. Typically testing will result in a "power factor" rating which determines the color rating. Also... you should not load a PSU with more than about 75% of its listed rating (as a suggestion).
But this does not tell you how clean the PSU is. I dont mean how much dust it has inside either. The primary enemy of computers is something called ripple. During the conversion of AC to DC there will be some level of the unwanted alternating waveform remaining due to inadequate filtering and suppression. You will know if you have ripple in your PSU because it will cause your audio line to have a constant buzzing or background tone. It can also cause MB capacitors to age prematurely and worst case scenario cause HDs to die very quick deaths with constant data loss. This is why you should never skimp on PSUs.
Fortunately when it comes to PSUs you have three friends. Anandtech.com tests PSUs regularly and they post reviews. You can also buy a oscilloscope and learn how to use it. And thirdly you can post the type of PSU you have along with a list of every device you are running (and I do mean all).
Or you could visit the manufacturers site and use their PSU calculator. Just about every manufacturer has one these days.
EDIT: Have a nice day.
