No worries
That's bad about the motherboard. Not even posting sucks. You've no doubt tried this already. Is power getting to the board at all? It's not the PSU? if there's no signs of life anywhere you could connect a fan by molex and jump the 24pin like when you test for leaks if you don't have a psu tester. Or try hooking up the PSU to another PC - it can at least rule that out. I had a PSU fail but the symptoms all showed up elsewhere. Instability, Drive failures etc.
I don't see how changing your cards can blow the motherboard unless the slot is actually damaged maybe or if it was powered up when you did it.
Haven't bumped any ram sticks or other components that may have come loose? My RAM latches sit pretty close to the back of my cards so can unlatch if I'm not careful moving things around so could be worth a look. Even then you'd have to be extremely unlucky. Does your mobo have an extra SATA power connector somewhere? Once again tho that's generally more for overclocking and stability iirc not to actually get the board to work.
That's the worst timing too. Just when you want to try out your new cards as well.
Maybe Dice's luck is contagious?
Good luck with MSI.
Edit - Keen to see those 980Ti's with the MSI bridge connected. Should look the goods when you get your new board.