Its not breanding that matters, its manufacturer.
The problem is reliability and ACTUAL wattage available. I doubt that 500W unit could even deliver 500W.
A cheap unit is likely to fail and take most of your system with it, a more expensive unit has protections in place to avoid these kinds of issues.
What are you looking to spend on a PSU?
Is that so? So to be sure i really have to buy new one then. Could you give me a good 500w psu which would not cost me more than a 100 bucks?