Considering that the system you are building is on a very limited budget, I'm hazarding a guess that it has only one mid-range gfx card, a single HDD, a mainstream processor, 4 GB RAM (max) & not too many bells & whistles. Now for all this, 650 W will be too much, even 500-550 W would be more than enough. You do have some excellent choices within that price range (I probably don't need to tell you that).
Going off the comments in those links I would say stay away from Rosewill. The Cooler master seems relatively new, so it's longitivity is unknown. The OCZ seemed to have the problem of dying on lots of people. Choice is your's.
What are the specs of this "cheap" system? For all we know, you might be fine with a 350W sparkle. Works well, nice and quiet too. http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Provides between 200 and 350W on the +12V rails. I couldn't find a specified number but it shouldn't matter unless the system has a GPU or like 6 hard drives.
And yes, OCZ is not a cheap brand. They are actually good and are often lower priced due to all the mail in rebates that seem to crop up for their PSUs. I got my 600W for $30 or $40, I can't remember which.