the MSI board is a micro-atx board, and is mainly gonna be used for OEMs/media centers and such. It's not meant to be an enthusiast board, as is evidenced by its lack of PCIe x1 slots.
As for those X850s, I can't really say I'm excited about them, given it's just a 3% clock boost, and they have to resort to dual-slot to accomplish it. Plus, the price of admission will go up $50, so you'll actually be getting LESS performance for your money, since for the old price ($450) of an X800XT (non PE) you can now only get an X850 pro, with a lower fillrate. Same goes for the X800XTPE versus X850XT (non PE). I know refreshes aren't usually that great, but usually they are a little more substantial than 3%, or at least add more memory. After seeing performance jumps of literally 100% or more with the NV40/R420 generation, I'm just not excited about 3%.