first off, as far as what psu, you cannot go wrong with pc power and cooling. depending on what all your running, you can pick the model that best suits you, but they will make a model that'll do the trick. for referance, i use their 470 silencer psu, although my computer isnt on 24/7, but i am very happy with it non-the-less
as far as other required hardware, for the basics, ample air flow, good, solid heatsink/fans and you should be good. oh, and dont forget warrenties. make sure whatever you get has a good warrenty.