I just bought a used Sapphire Radeon RX 580 for my cMP as well I havea NVMe drive in a PCIe adapter. I am going to put the GPU in slot one, would it make sense to put the NVMe in slot 2 if it will fit, or should it go in 3 or 4? Right now I have a traditional SSD on a PCIe card I that I am booting off of, eventually I want to boot off the NVMe.