I would increase the RAM to 16GB minimum, 32 better, 64 GB best. Since you are getting an i5 you may want to go with DDR4 2400 since it will be more price effective.
As far as Sierra goes, do a search here for your mobo and see if someone has a "[SUCCESS]" flag in the title. Since you are not upgrading from El Cap you may have more success than I've had. But if you need Windows to be installed quickly (instead of waiting for Sierra to be installed correctly) you may want to install Windows and OSX in Legacy mode, although UEFI will probably provide a faster boot up. Deciding which method to use is a big decision. (I went with Legacy because it allows me to move disks around, for instance I now am running W10, OSX, Mint MATE Rosa (17.3) and Mint KDE 5 on separate drives and I can play with other Linux distros if I so choose. Sierra is a pain because it uses the UEFI/EFI partition and since I already have El Cap installed upgrading Clover on the Sierra drive will automatically update Clover on El Cap.) [Side note: installing Linux Ultimate Edition, KDE Nuon and Mint KDE 5 caused all sorts of problems, problems which I finally traced down to BIOS settings, so maybe I'll now be able to install Sierra correctly.] So it really depends on how flexible you are going to be. On that note, don't be surprised if you experience the typical additional UEFI entries problems and the coming out of Deep Sleep problems, which I associate with UEFI (yes, I could be completely wrong in making that assumption - but then again, I don't use Deep Sleep, Sleep or Hibernation on my systems.)
The reason for installing OSX in UEFI first is so that it installs the EFI boot loader on the OSX drive and if Windows decides to update or upgrade itself it hopefully won't mess up the EFI boot loader, which would mean that you could then not be able to boot into OSX.
Idk about your choice of PSU since I only do Seasonic. Same goes for fans and heatsink, I only do Noctua.