New system not booting

Was unsure if this was the correct section to post as windows has not been load yet.

To the problem, I recently started building a new system for my brother.. Specs ill put in dotpoint form underneath.

*AsRock AMD 970Pro3 Motherboard
*AMD FX 6300 3.5Ghz 6 Core CPU
*Patriot Viper 1600 RAM
*Vantec ION 520W PSU
*XFX ATI Radeon 7770 Graphics Card
*Various hard drives..

Time to boot.. Nothing comes up. Fans spin, led's light up, though nothing comes up on display, nor any beep. Attach a motherboard testing card. Comes with 0.0. After various tests I perform on it mixing different hardware to get to the bottom of the problem. Still the same problem. I get convinced that it is a problem with the cpu or motherboard so I take it back.

Apparently its the BIOS, CPU needs version 1.5 BIOS, so they update it for me. I pick it up, bring it home and yet again, the same problem. I bring it back, they test it.. Apparently it works and windows loads.. Yet I still can't boot it at home.

I notice that I didn't try different RAM, so I try that, to no avail.

Any ideas?

Replace the motherboard

Its apparently been checked by the computer store and said to be fine. If I had another amd socket am3 motherboard in the house I would test it out anyway, but I don't. Must find another solution.

Take it back to the computer store once more and be forceful in telling them it still won't work properly. The store isn't Best Buy is it?

Its from 'MSY' in Australia haha, they're not known for their customer service skills, but they're prices can't be beaten. Guess that might be the only option

Okay Ural, I wish there was another option... Maybe power supply?

I tried another power supply I had at home, however same problem. Although this was only 350W, do you think theirs any chance that it could just need a very powerful PSU? Well over the 500W?

Yes you probably need a bigger power supply. The reason I mention power supply is because it is really the only part that may be affected by where the computer is plugged in. The computer store or your home

The computer store used their own, so you might be correct, is their any good way of testing if a power supply doesn't give enough power to the cpu itself?

Or atleast the motherboard, since the fans and drives seem to be powering on fine.

No you have to swap the PS out with a better more powerful one