Crashman :
Right now Gigabyte has the best lane configuration and slot spacing four four cards, MSI has the best lane configuration and slot spacing for three. Gigabyte has the USB 3.0 header blocked by a fourth card, MSI has the three cards + PCIe x4 M.2 +USB 3.0 configuration nailed (if you care about PCIe x4 M.2). You'll see another MSI board in a review still pending its publishing date.
That about summarizes it - thanks! I'm looking at a 5820k based rig. Long term goal is water-cooled 3-way x8 + PCIe x4 M.2. So, MSI has that configuration down. Shorter term would more realistically be air-cooled 2-way, and my understanding is the MSI is not the best for 2-way air cooled due to the slot spacing.
So I think I'm looking for a board that can do both a (1) dual SLI x16/x0/x8 + x4 M.2 or (2) 3-way SLI x8/x8/x8 +x4 M.2, all at just above $200.
The lowest price board I could find that can do this is the ASRock x99 Fatal1ty Pro or OC Formula, both in the $340-350 price range. The Professional happens to have a $40 rebate plus $85 DDR4 combo discount, making this a ~$220 proposition for this board. Tempting......
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157539