I definitely agree about Raidmax - awful brand. But I would not recommend the Gaia - too many cheap and loose parts, and with the thermal "paste" (term used loosely) included I lost a motherboard. Spend a bit more and get something better like the Noctua NH-U9B. I had the Gaia and after it fried the motherboard I was using (Asus M487TD Evo) it is now being used as a paperweight on my desk. :lol:
The Antec is good but 500 would be a bit underpowered for OC'ing and a 560. EVGA recommends minimum 600W, 650 just to be on the safe side.
And as far as overclocking goes - I only recommend it if you know exactly what you're doing - IMO it's really risky for minimum payoff and I wouldn't recommend it if it's a first time build.
I would upgrade the PSU first because the PSU is the "heart" of your computer, if it fails then it could potentially damage your whole system by frying components such as the CPU, RAM, and MoBo. Even if it doesn't fry the components, if it fails during a write operation, it could corrupt your HDD, so I would highly recommend changing the power supply. The RaidMax PSU you chose also isn't 80+ certified, therefore, the manufacture could be making the numbers up. Some PSU makers would rebrand lower PSUs as higher wattage ones since the wattage shown is the highest wattage output by the PSU and most times it doesn't even reach close to those watts. By making the PSU 80+ certified, it means that you know at 100% load the PSU will be 80% effective.
Totally agree and that's where it gets really tricky with PSUs. The bad thing is when you find a wattage for a price range where the higher end models are significantly more (example - a 700W PSU for $50 where higher end models run $100), that should be a red flag as it's a significanlty cheaply made model. The thing is it's the key to stick with the known manufacturers (Corsair, PCP&C, Seasonic, Antec, etc) rather than venturing into ones that aren't as well known.