If you go gold or platinum rated, you'll typically only use a max of around 200-300 watts. You'll also save a good deal of money per month depending on how often the PC is on. You aren't gunna find one for under $75 though but you'd be better off waiting a couple weeks or however long to get a more reliable PSU. The importance of a good reliable PSU is often ignored.
Yeah I would still get 550-700 gold/plat. You definitely don't want too little but more often than not, people get way more than the recommended safe margin.
As an example I idle 100-150w, max 300-350w on a 760w platinum PSU running a 4.5ghz amd fx 6350 with a r9 290x, 4 drives, and 4 sticks of memory.