I've had this setup for a little over a year now, have made various upgrades during this time as well.
My computer refuses to POST, I get no beeps, I get no power to my USB devices, my VGA seems to be recognized but there is nothing other than a black screen, no bios.
All of my motherboard and case lights work, all of my fans are spinning, but that's pretty much it.
I have tried CMOS reset via battery reset and jumper reset. I tried replacing with a new CMOS battery. I tried booting without memory, I've tried booting without a CPU for 10 seconds (this is supposed to reset the bios) and then booting with CPU, this didn't work.
I doubt that my PSU is the suspect here simply because I've upgraded it relatively recently (less than 2 months ago).
I am about to try booting outside of my case in the off chance that it is causing a short circuit somewhere.
Can you try it with the PSU you replaced? I had something very similar happen about 2 years ago. Replaced mobo and cpu, and it didn't fix it. Sent those back and decided to build a new box. Still don't know exactly what the cause was, but I'm suspecting it was the PSU.