The PCIe 3.0 lanes are straight from the CPU and can only do either x16 or x8x8. The third x8 slot would be from the IO Hub's x8 PCIe 2.0
If you want to do x16x16x8 all with PCIe 3.0, you would need go get an LGA2011 SB-E CPU which has 40 PCIe 3.0 lanes.
Thank you for the reply! Just checked into it and seems the best route, hence how I am seeing x79 boards with more lanes. Main issue here is no TRIM support for any chipset supporting LGA 2011 on SSD RAID 0. I keep reading how x79 is getting it 'soon' but you know how that works out.