MSI Z97 Gaming 5 - 00 (D0) error, no output after fried video card

I'm hoping someone might have some thoughts as to my current situation, and if there's any possible answer besides my motherboard being fried. I apologize for the long post.

Components:

• 
  CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor
  CPU Cooler: be quiet! Dark Rock Pro 3 67.8 CFM Fluid Dynamic Bearing CPU Cooler
  Motherboard: MSI Z97-GAMING 5 ATX LGA1150 Motherboard
  Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-2133 Memory
  Storage: Crucial MX100 512GB 2.5" Solid State Drive
  Video Card (orig): EVGA GeForce GTX 780 SC
  Video Card (new): EVGA GeForce GTX 970 4GB SSC ACX 2.0+
  Power Supply: EVGA 850W 80+ Gold Modular ATX

I built this computer about a year and a half ago, and it's worked great for the entire time. About a week and a half ago, I was playing a game with my wife and all of a sudden my computer completely shut off. Just as it did, I realized something smelled burnt. I immediately unplugged the computer and left it for a bit.

I tried turning the computer back on afterward, and it wouldn't turn on at all. It would 'click', but nothing would power up.

I opened up the computer and tried to locate what smelled burnt. This led me to first thinking that it was my PSU, which seemed logical to me (since nothing would turn on at this point).

I ordered a new PSU and tried replacing it, but it didn't help. I then put my old PSU into my wife's computer, and that worked fine. Checking my computer again, I realized the GPU smelled even more 'burnt' than the PSU had.

I moved the old PSU back to my computer and removed the GPU. After doing this, and finagling with the computer a bit longer, I got the computer to boot, and it worked just fine. I've been using it without a discrete GPU for a week and a half now without issue.

Thankfully, my GPU was still under warranty, so I shipped it back for an RMA. The replacement just arrived today. While it's a newer model, PC Part Picker indicates I should have plenty of power for the new setup.

I plugged in the new GPU, and once again the computer wouldn't boot. It comes on for a split second (the fans spin, the motherboard briefly lights up), and then powers off.

I removed the new GPU again and tried going back to my old setup (no discrete GPU). It still doesn't boot. Once in a while, it does actually turn on and stay on; however, the two-digit 'error code' LED reads '00' (or 'D0', as someone else mentioned on a similar Gaming 5 thread). There's no video output either, but it will stay 'on' like this indefinitely.

I've tried resetting CMOS (fully removed battery for ~10 mins), which did result in the current 'on but stuck at 00' stage, but hasn't gotten me any further.

I know I should try breadboarding and testing each component, but I don't have a good setup for this at my house right now. I'm worried about further damaging the system if I don't have a good environment for having the components out of the system.

The fact that it ran just fine after this incident with no GPU for well over a week also makes me puzzled. Why would the computer work fine after this issue, but then die again with a new GPU in place (so badly that it's now seemingly unrecoverable)? That might not be a question that can be answered, but I guess I'm mostly looking for ideas at this point.

Anyway, if anyone has any thoughts as to what more I could try, I'd greatly appreciate them. I'm thinking I might have to get a new motherboard at this point, as a brief internet search indicates that the '00/D0' code seems to be a harbinger for a dead board, but I'm hoping I might have another option or two to try first. Or, if not, I'd like to learn more about what happened to my system, and what I should do in the future if something like this occurs again.

Thanks!