Not to interrupt the flow of troubleshooting, but...I caved! Picked up the Asus X670E-I motherboard and RAM today. I'm so excited: in all my years, this will actually be my first system put together with an entirely new motherboard and entirely new cpu. So what did I do first? Tear it apart to swap out the wireless card for my Broadcom one
At first, I was pretty shocked at how easy access to the wireless card was- just a couple of screws and the plastic bits came off and exposed the wireless card and enclosure. But the tricky part was that the CMOS battery and the ribbon cable connecting to it were stuck on to the side of the wireless card enclosure with some sort of adhesive. I had to be
extremely careful peeling it off that I didn't rip any of the cables/leads. The VRM fan cables are also pretty thin too. Just a heads up for anyone else who wants to attempt a swap!
Just put everything back together, hopefully it's all functioning! I'd hate to have to go back in there again haha. Can't test yet though, CPU still on the way!