New mobo, CPU, RAM; won't POST

Couldn't find your sticky you mention under motherboards so not sure what that says. Sorry if this is a repeat of that stuff.

CLEAR CMOS (sounds stupid I know)
Turn off the PSU's power switch (if there is one, generally this cuts board power & LED's should go off if there is an LED somewhere on board letting you know it has power still flowing, but being paranoid...), disconnect the power from the PSU also (I'm talking the cord that goes to the wall here), disconnect power and data cables from all drives, they are not needed to boot and get into the bios. Keep one module in whatever slot the board says is Dimm1 (seems DDR3_A2 for you), remove the battery and clear cmos (10secs or so with jumper for clearing cmos shorted). Plug the power to the PSU back in (flip the switch on if there is one on the PSU) and power up. The odds you have TWO dead dimms are pretty much ZERO if you are aware of ESD and how to handle parts. I wrote the below stuff and then just decided to put these steps above it to simplify things for C_CMOS (not knowing how much you know about PC's)... I'll leave the below stuff for someone else having issues that it may benefit and you may want the memory info if you get into the bios after clearing cmos. If it's not cmos read below for everything you should pull to get a boot (basically every non necessary cable...LOL - 4th paragraph I think below).

Memory can be set up pretty much no matter what it is if you go into the bios and manually set the timings (they should be marked on the ram, but if not you can generally find the model online to get them). On the rarest occasions I have actually known of some literally incompatible memory but not often and in those cases the manufacturer of the board usually literally calls them out as incompatible or the memory maker says "incompatible with X board" (the compatible list just means they tested that module, not that those are the only ones usable). SPD's are notoriously unreliable IMHO (I owned a PC business for 8yrs and have multiple certs and probably a few thousand builds, so I have seen MANY boards and brands), and I personally always set the memory manually. I trust no board/SPD to do my job

The cheapest thing to do here and fastest is clear cmos if you haven't done it. Pop out the battery and clear it with a jumper. If you can't find it clearly marked (odd) you should be able to find the manual for the model online if you don't have one. I've had many boards that wouldn't just figure things out on their own if it was a board previously set up on an old cpu. Clearing the cmos fixes that if it's just that simple and at times I've needed to do that on boards I THOUGHT were new but were really RMA's that had already been setup for someone's cpu and returned (I didn't buy from those distributors for long...LOL). I say that because you said you had it running and are aware of ESD so I'm assuming (could be wrong, did you take the same ESD precautions before problems?) you didn't damage the parts yourself. You may have just set something that it isn't able to recover from (wrong hypertransport speed/ratio etc) - many things can make you unable to boot back up if you were playing in the bios before it became unbootable.

One more note, I've had a board not boot because I had a few pins reversed on USB ports (long time ago with they were not 10pin blocks etc, but lots of single pins, same for audio headers). You might check your leads on reset/power too. Or just pull everything not necessary (all usb, firewire etc onboard+ front panel ports (audio, usb, firewire etc), floppy data cable & power if you have one (I've seen a backward floppy cause a no boot situation also), HD's, CD, etc yank all power and data from them all and maybe just have power/reset hooked up for system panel (hot leads should be indicated on the BOARD and at times the manual is WRONG, always believe the silkscreen on the board vs. manual). Only have what is necessary plugged in to get video up. If it works, add things one by one until you die again which will point out what is stopping the post. So Vid/cpu/memory in DDR3-A2 slot only and of course power to cpu fan/psu fan & power to the board with the power switch hook up also (technically you don't need reset to boot). You don't need any LED headers hooked to boot either.
"Please install the memory module into the slots DDR3_A2 and
DDR3_B2 for the first priority"
I guess they want you to put them here first, so I note DDR3-A2 above for single (page 14 of QIG).

http://www.asrock.com/mb/AMD/990FX%20Extreme3/?cat=CPU
IF that's right, all thuban's should run with any bios according to the chart for your board.
http://download.asrock.com/manual/qig/990FX%20Extreme3_multiQIG.pdf
ClearCmos #22 on page 2 of quickguide.

Hope that helps, I see you already tried the known good psu.