No post even after breadboarding.

with your issue make sure there nothing shorting out the mb. pull the gpu see if the mb will power up and see if the gpu or any of the fault led come on. if not ask a friend for a test power supply. first rule of bench marking is you need to know if you have good power. if there no post with a known good power supply i would rma the mb first. most times it can be vrm or a cap failure causing the mb not to post. with intel cpu you have to over clock or short there cpu for there cpu to die before a mb will.

Two items to check.

A case usually comes with stand-offs pre-installed in threaded holes on the back mounting plate. These are small metal spacers about ¼" high with a threaded hole in the top, and you screw into them the screws that go through the mounting holes of the mobo. Each mobo has a set of such holes, often three rows of three each, but each mobo type has a slightly different layout. So the case back plate has several extra threaded holes for the stand-offs and you MAY need to move those items so that they match exactly the hole layout of the mobo. Of course, to do this you need to remove the mobo from the case, but first examine the holes from the mobo top and see whether you can spot any odd placements. Ideally, there ought to be a stand-off under each mobo mounting hole for support. But MOST IMPORTANTLY, there should NEVER be a stand-off under the mobo where there is no matching mounting hole in the mobo. A mis-located stand-off can short out a trace on the mobo bottom side, causing symptoms as you describe. A mobo is designed to be grounded to the back plate at its mounting holes ONLY, and never at any other spot.

Second idea. You say you did a complete breadboarding operation, but no details. Breadboarding is a systematic troubleshooting technique with a particular sequence of trial and error. To do it you start by removing the mobo and add-ons from the case and placing it on an insulating surface like a dry board. Then you strip out all but the very basic add-ons. You should leave installed on the mobo only the CPU chip and its cooler and ONE stick of RAM. Connect to the mobo the main power supply cable from the PSU plus any power connector for the CPU, and ensure that the CPU cooler is connected to its mobo header. Then connect a signal cable from the mobo's video output socket to your monitor. Look in your mobo's manual (p. 12 and 16) for the pinout details of the Front Panel header at bottom right and locate the two pins (6 and 8) for the Front Panel Power Switch. Turn on the power switches on your monitor and PSU. Now briefly short (small screwdriver) the two header pins for the Power Switch. A short for only a second should turn on power and start the POST sequence. That takes a short time and ends with some beep signal (IF your mobo has a small PZO "speaker' for the beeps). It also should produce a few messages about the POST process on your monitor screen, but end with an error about nothing to boot from.

If you get that far, you have a good basic system and PSU, and can proceed to the next step.

If that worked and you DID see messages on your monitor screen, skip this paragraph. But there may be a snag for you with the video connection. You had our system working with a video card added into a PCIe slot. So your mobo may be configured now to use that output device, and not any on-board graphics system. In that case, you may not get any signal from your mobo's output connector to your monitor. If that happens - that is, if the initial POST process appears to complete but you get no monitor messages - shut everything down and disconnect the power cord from the wall to your PSU. Now look on your mobo for the silver battery about the size of a quarter in a plastic holder near bottom centre. NOTE its markings so you know which way it is mounted in the holder. Now look just above the Front Panel header for a small 2-pin header labelled CLR_CMOS. Remove the battery and short together those two CLS_CMOS pins for about 10 sec. Un-short them (sometimes there's a jumper to move) and replace the battery right-side-out in its holder. This will reset the BIOS custom settings to factory defaults, and that includes making it use the mobo's video output system. Then re-connect power and try the start-up, and you should see messages on your monitor.

If you get a clean POST up to an error message about no boot device, that collection of components is OK. Now start a stepwise sequence of adding ONE component and trying it all again. Shut the system down by turning off the switch on the PSU. Then turn it back on.

1. Plug in your keyboard and start up again by shorting the two Power Switch pins. If you get a clean POST completed, then the keyboard is OK, too. Shut down.
2. Connect your mouse. Start up, check, shut down. If OK, proceed.
3. Add in one more RAM module, start up and check. If OK, shut down and proceed.
4. Add any more RAM modules.
5. Keep on, one addition at a time, until it fails to POST. Next item can be your HDD, and this time it should actually succeed in a full start-up since it has a boot device. IF it does not, shut down and re-start BUT hold down the keyboard "Del" key as you do so that it is forced to enter the BIOS Setup routines. See your mobo manual on p. 26. You can tell it exactly what device to boot from, then SAVE and EXIT and let it finish booting. If you get this far, from now on you can shut down by using the normal keyboard or mouse actions to do that.
6. Next step install your video card in its PCIe slot then boot. According to your manual p. 31 it should automatically detect that card and start to use it. So, move your video cable from the mobo's output to the video card's. If that is OK, ignore the rest of this "step" and proceed. But IF you get no display on the monitor, move that cable back to the mobo socket to get the old display. Shut down, reboot and again use the "Del" key to enter BIOS Setup. See manual p. 31 and set it to force use of the added video card, then SAVE and EXIT to reboot that way, and move the video cable back to the video card output.
7. If you can get the entire system to boot and run smoothly this way on the dry "breadboard" with all your components added in one at a time, the hardware is OK. Then the thing to look for is what is not right in the way all that stuff gets installed in the case. One of those things is that question about stand-off placement.

At any point in the sequence if the system fails to complete the POST process, you now know where the problem lies. It it was at the very first step with only the bare minimum components installed, one of those is the problem. If failure happened later, the most recent addition is where to look.