I'm planning to upgrade my build to support 3 monitors, but I only have a 500W power supply. I'm looking at this graphics card http://www.ebuyer.com/product/222056 , it says its minimum power requirements are 500W and that's the same as my power supply, I'm just wondering because the other components use electricity too, does that mean this will overload my PSU? I'm also worried because that's the minimum, I'm planning on running 3x1920x1080 monitors on there.
So my main question is, will this work or should I get a different graphics card or worse case scenario a new PSU?
The PSU requirements are for the system as a whole, not for the card alone.
What PSU do you have? A decent modern 500W unit will support the 5850 without a problem, but if you have an old unit it might have some issues. If you dont have a good PSU, getting a nice unit is a good investment as it will last you 5 or more years.
They arent nearly the best, there are many that are far better, but the Sonata III comes with an EA-500 which is plenty to support a 5850 on, you dont need to worry about getting a new PSU for a while, i have one running my system, they are good little units.
The GPU isnt going to kill the PSU, capacitors age over time so after several years a PSU needs to be replaced simply because its too old, it should make it at least a few more years without any problems.
Are you planning to game across all 3 or just run apps across all 3? If you want to game across all 3 it might be a little iffy, thats a lot of load even for multiple 5870s, but if you are just using it to run 3 monitors for regular apps it will be fine.
WoW and Runescape arent super intensive so it should do well, you might need to turn down settings a bit or move to one monitor for WoW at times, but it will work, if you wanted to run something like Crysis across 3 you would need more horsepower but it should be able to do WoW well, and for the time when you are running normal apps it will work great.
Its not going to hurt the GPU, you will just get like 10FPS if you try to play across all 3 on high making it pretty disappointing. For the most part, you arent going to manage to damage hardware with software unless you really try.