I know this can sound a bit rediculous, but I have had issues where a brand new motherboard will not boot unless I clear the CMOS. It's one of the simpler tests/fixes you can do too.
If you have a manual for your motherboard, lookup how to do this as some motherboards have a backup capacitor for when your changing your battery that sometimes needs shorted.
Otherwise, unplug your machine (This needs done, otherwise the 5V+ auxiliary supply will keep the CMOS memory powered), remove the battery from your motherboard, go and chill for 10 minutes - have a coffee or something. Come back, replace the battery, plug it back in, and attempt to boot. It might take a bit longer depending on what the default BIOS settings are.
I second/third/whatever it is now: the suggestion that you check your memory (Ensure it's seated right) and CPU cooler. People are human, and mistakes happen. To assume that the builder is incapable of making a mistake is a bit of a folly. If none of this works, the Power Supply should be the next thing to look at...
Now the good news is, that combination of motherboard and CPU means that you have onboard graphics. Rip out your discreate graphics card, and use the onboard graphics. See if this lack of load allows the system to boot up. If it does then there are three possibilities: 1) The Graphics card has some flaw in that is it taking too much of a load that it is tripping the power supply, possible short? (The motherboard would, in 99% of cases, continue to boot with a dodgy graphics card), or 2) the powersupply is simply not able to handle the load and the 600W label is a bit of a gimmick (Or simply not high enough - I don't know the estimated load of your system from the top of my head, but I would expect that 600W should be enough), or 3) your Power Supply is simply faulty.
Try the Graphics card in another machine, and try a different PSU.
Report back if you can, and we'll take it from there.
---------- Post added at 09:00 AM ---------- Previous post was at 08:55 AM ----------
Another thing, what model number is your Seasonic Power Supply?
Does it have a single +12V line, or more than one. If so, you need to ensure that you're not pulling all the amps from one line - as this will certainly overload that particular line and no-doubt trip the PSU.
Please supply a model number and I'll look this up. You want to power the motherboard and Graphics from two different +12V lines if possible, and if your graphics card takes more than one 6/8pin supply, try and take each supply from different +12V lines.
If you only have a single, monster +12V line, then this shouldn't matter, but we'll need the model number of this to confirm.
