Note - In case you're wondering, this process is not a strictly linear progression. I suggest you read through it first before you do anything else. If you look around in this forum or elsewhere online, you'll find lots of alternatives methods, this is just the way that makes best sense to me. If you think I'm smoking dope and want to use a different method, feel free.
Okay, go into your BIOS, and on the Main menu ensure that the BIOS version listed is 2501 dated 2014/05/14. While it's still in BIOS, hit the MemOK! button next to your DIMM slots in the upper right hand corner of the mobo. When it's done going through it's routine, the DRAM LED should go off and stay off (if it stays lit, there's a DRAM issue), then post and logo screen should come up again on the monitor.
At this point, you can try to boot to Windows, but I would recommend you go ahead and do a clean install. I know you've already done that, but if you're dead lucky, the problem involved a conflict with the original BIOS, and a BIOS update, clear CMOS and fresh OS and driver install may take care of it. Once you've gotten Windows installed, go ahead and install your basic drivers. I'd recommend downloading all of the latest drivers from the website rather than loading them from the support CD, then installing them with a thumbdrive in one of the USB 2.0 ports. You'll want to download the following Asus utilities also: EZ Update, PC Diagnostics, Asus Boot Setting, and CPU-Z. Finally, download AIDA64 (30 day free trial) and Sea Tools for Windows.
http://www.seagate.com/support/downloads/seatools/
http://www.aida64.com/downloads/aida64extreme460exe
If your PC hangs up, crashes or shuts down prior to or during the loading of Windows, then it probably is a hardware issue. Without onboard graphics, one way to see if it's the GPU is to try it in a different machine and/or try a different card in yours. Same deal for the PSU - the only real way to verify if it's the problem is try it out on a different PC and/or try a different one on yours. The best way to check the ODD is just to disconnect and run the PC without it. The HDD can be disconnected and health-checked on another PC.
When you load the drivers, do them one at a time and reboot after each. Once it reboots, before loading the next one play around on Windows (open and close folders, play the video samples, move some files around, go through control panel settings, what ever) and see if you can induce a shutdown. If you don't get anything, go ahead and load the next one. Save your LAN driver for last. If you get a shutdown at any point during driver loading and installing, make sure to note what driver was being loaded and any pop-ups, warning messages, etc that show up, if any do.
Once all the drivers and utilities are loaded up, but before connecting to the internet, install and run PC Diagnostics, Sea Tools and AIDA64 Compatibility Test. Let the AIDA Compatibility Test run for at least 20-30 minutes but preferably an hour or two. During the testing, keep an eye on your CPU temps until they stabilize. If it passes all of these without shutting down, install your A/V and connect to the internet and run EZ Update, reboot if necessary, then try updating Windows.
This whole process will take a while and will be tedious, but the idea is to be meticulous about it. Hopefully the process itself will eliminate the problem, but if not, the various steps and tests should be able to either identify the source of the problem or at least drastically narrow down the possibilities.