Well, I don't know if it's good news or bad news, but it sure is news. XD
I unplugged some more peripherals (while the PSU was unplugged) and booted it up to find that I had onboard HDMI output to my display!
I was able to enter BIOS and found that it listed my CPU and RAM correctly. Excited, I checked to see if the VGA led error light had gone away; and, it had! However, the Boot error led was alight, when it had not been before.
All the fans were running, the CPU idle temp was a stable 21 *C and the power was not fluctuating. I tried restarting it a few more times, but the Boot error led persisted.
So, now I have taken it all apart again. I am going to try again, OUTSIDE of the case with only the bare minimum components (cpu air cooler included). Then I will add the other cables one at a time, powered down, to see if I can isolate the Boot problem when/if it shows up this time.