I am probably going to use 2 750 series from Intel (1.2TB each), along with a dual SLI configuration (not sure on the graphics cards yet). After reading the manual (link below), in order to have a working SLI configuration you need to use the 1st PCIE_X16/X8_1 slot and the 3rd PCIE_X8/X4_3 slot, resulting your SLI running at x8 [page 1-22 and 1-23 from the manual]. I would also like to mention that I will be water-cooling my build. I want to believe that there will be enough space for a possible SSD to be placed in between the Graphics cards on the 2nd PCIe 3.0 x4_2 slot.
https://www.asus.com/Motherboards/MAXIMUS-VIII-EXTREME/HelpDesk_Manual/Something that I was not able to find in the manual, is how will I be able to get the maximum performance from the SSDs (given there is no software limitation). I know that the first 3 slots go through the CPU, and the 4th slot goes through PCH, and to be completely honest with you I do not know what does this mean. It is also mentioned that the 4th slot initially runs at x2, where if you change that to x4 you disable your SATA6G (which I will not be using, thus i do not mind) "SATA6G_56 will be disabled when [X4 Mode] is selected." [page 3-32 from the manual].
Both the 2nd and 4th slots are capable of running at x4 - PCIe 3.0 x4_2 slot and PCIe 3.0 x4_4 slot respectively
As I mention in the title of the post I will be buying 2 750 series 1.2TB drives. My question to you is "Should I get them both in PCIe type and place them in slot 2 and 4, or should I get one in PCIe and one in the 2.5in model using the U.2 port, and if so, in which lane should I place the PCIe SSD in order to prevent interference with the U.2 lanes?
There is a "U.2/M.2/SATAEXPRESS1 configuration" in page 1-23 of the manual, but I am not sure I understand it. (if that helps in any way in my case)
Something that just came to my attention - I will also be using a 6700K i7 CPU which only has 16 PCIe lanes available (link below, find the information under Expansion Options). Does this mean that in case I have a dual SLI configuration (thus using 2x8 PCIe lanes) will I not be able to the 2nd slot, but only use the 4th slot which goes through the PCH. And if so will the SSD on the 4th PCIe slot and the 2.5inc SSD in the U.2 port conflict for bandwidth?
http://ark.intel.com/products/88195/Intel-Core-i7-6700K-Processor-8M-Cache-up-to-4_20-GHzI know this is a long post, and I apologize if I do not make sense at times. Thank you for the time you took to answer. I appreciate any answers and suggestions.