I've deleted your other thread - best to keep it all together here. If you're not getting a response, please just bump the current thread rather than starting a new one.
What I meant about the switch was a switch on the back that will turn the PSU completely on or off, since you probably don't want to go to the effort of wiring up a power switch, and just pulling it out of the wall isn't the best solution.
There's no real need to worry about the quality of a PSU or its output capacity for the sort of thing you're looking for, so I'd be inclined to go with about the cheapest one that meets your needs. Something like
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170018 would be good since the 120mm fan would be quieter than the smaller 80mm fans found in most PSUs.
One other thing to consider - you
may need to put some sort of 5V load on the PSU for it to work properly.