i have always used 1 good qualaty psu per rig but good psus and you can sell for 80-90% when used
if you want a good cheap psu buy hx/ax seris psus u can get 500w hx series on ebay for 30 or so
That is why I want a good quality one even if low wattage, so it holds the value.
If I didn't have the server PSUs, that is the route I would have gone.