I think you may need the 8-pin/4-pin for the CPU... Just check every cables if it's plugged in including the CPU Pins... By now you should realize that but if you did checked every cables, than it must be the PSU itself as some or few people got problem of it's not starting or dead on arrival... I woulda have gotten the Corsair Tx 750W V2 which is at same price and is better... If the PC start than turn off than start and turn off by itself than it's the 8 and 4 pin plug on the cpu(Next or near to it)...
He doesn't need a PSU with higher rated power output; that build could run on a 650TX, probably even on less than that (although it's a pain to find good PSUs at that stage).
Okay, so you've checked your wiring, do you have any other PSUs which you could use? It sounds like either a bad PSU or a bad mobo (or an incorrect setup - do make sure you double check everything), the easiest thing to do would be to try and plug in a different PSU and see if you can boot into bios.
Alternately you could take out a multimeter and start checking voltages: check your manual for detailed information on voltages then switch your PSU on and measure the relevant voltages across your mobo.