There are bad news, times two.
1) That EVGA unit which you got, is what model? 600 W1? It also could be 600 N1. In any event, both models are the bottom of the barrel in EVGA PSU lineup and worst offered by EVGA. Both models, at best, are low quality PSUs. Just a tiny notch above crap quality PSUs but nowhere close to a mediocre quality PSU. So, there's that. For equal comparison, you can look towards Corsair VS series.
EVGA W1/N1 series, Corsair VS series and the like are PSUs that i wouldn't never put inside a PC, even if the PC is office PC without any dedicated GPU and where PSU never sees any high loads, let alone putting it inside gaming PC. Since PSU is the most important component inside the PC, i won't put anything below good quality PSU inside the PC, while great quality PSU is preferred.
2) 2nd and bigger mistake was buying that PSU from EVGA B-stock. Not sure if you read what's said on the EVGA site about it but what you got is a used PSU. And that is really bad news. With used PSU, you'll never know what kind of abuse it has seen before and if it even delivers safe voltage ranges specified by ATX PSU standard.
Also, your PSU only has 1 year of warranty since it's used. If you would've bought 600 W1 brand new, you could've got 3 years of warranty (600 N1 comes with 2 years of warranty at brand new).
If i'd have a choice between great quality PSU but used one or good quality PSU which is brand new, i'd go with brand new PSU every day of the week, even when it means that i'd be sacrificing PSU's build quality. That's how bad idea it is to buy used PSU.
So, here's your answer on cheaping out on PSU.
Also, looking from the specs above, you could've easily bought brand new and good quality PSU.
You have there 500GB HDD where PC can run without it. That saves about $20. 5x case fans? RGB i guess? Well, PC will do fine with 2x fans as well, 1x intake, 1x exhaust. So, without getting extra 3x fans, you would've saved about $15. PC case isn't needed for PC's operation at all. It's only to keep PC components safe from external damage and giving some eyecandy as well. Average PC case goes for $50 or so.
Let's add the savings together; $20 from HDD, $15 from 3x fans and $50 from PC case + $20 you spent for that used low quality PSU and we'd get: $105. $105 is more than enough to get brand new and good quality PSU, e.g Seasonic make,
pcpp:
https://pcpartpicker.com/products/compare/R7V48d,Tc3RsY,WrNypg,qn7v6h/
E.g M12II-620 EVO is at $70 and while it's a bit old platform, it's still a good quality PSU. My Haswell PC is also powered by M12II EVO series PSU but mine is 850W unit. All 3x of my PCs are actually powered by Seasonic, full specs with pics in my sig.
Or, if you wouldn't have bought the GTX 780 at $150 i guess, you'd have more than enough money for good quality and brand new PSU. Since you have Intel build, you can use i5-4570 on-board graphics to run the PC without issues. Sure, gaming wise it doesn't do that well but i'd rather have solid power plant powering my PC than that ticking time bomb in there.
Any more questions?