I think the time is approaching that I should be replacing my old 2008 model Mac Pro.

It's lasted a long time, handles almost anything I throw at it, including games, but it's showing it's age (due to it's early EFI support, SSD support in Windows is basically non-existant)

As I've been slowly moving away from OS X and Mac only programs I've come to the realisation that I don't actually need a Mac any more, so it's time to build my first PC in probably a decade. I still may want the option of running OS X, so for compatibility reasons Intel is the way to go here.

This machine will be a dual purpose system - for gaming and photo editing - on the Mac I'd use Windows for gaming, and OS X for photos (and music in the past) but with Apple killing off the program I was using and forcing me to migrate across to the cross platform Lightroom, I no longer need to worry about that.

I've been researching a fair bit, and I've decided on the following specs to aim for:
I've had a look at the different options from Intel, X270/X299 etc, and based on my budget and needs,
Intel i7 7700K (four cores/8 threads will be a close match to my current dual quad system, and I've barely ever maxed them out)
MSI X270 Gaming M7 - has enough I/O for most of what I want to do, with the option of Intel's Optane if it's worth it.
Corsair 2x 8Gb DDR 4 3ghz Ram - enough headroom to have a play if I need to, with the option of doubling the Ram later if I feel the need
Corsair 280mm AiO watercooler for the CPU.
Corsair Carbide 600Q case - Inverse ATX matches my Mac's board orientation (access from the right, not the left) so I won't need to swap my desk around, enough room for decent airflow and the water cooler, and it's nice and quiet (not looking to show off the contents)

Keeping my current GTX 960 card as it's decent enough for now, and I can always upgrade later when I can afford to.

Storage wise, thinking of getting 2, maybe 3 M.2 SSDs (hence the mobo choice) - 1Gb SSD solely for games, a 256, maybe 512gb one for the Windows install, and either a small one for OS X/Intel's Optane option. Might use a SATA drive for OS X if I go down that path.
I'll still have one or two HDDs installed, one 4tb unit for my photo storage pulled straight from the Mac and possible one of the 1tb drives for backup purposes. Tempted to get a small SSD (~128gb for "scratch" purposes - use it for any current photo projects for quick I/O, then "archive" them once a month, or whenever it fills up to the 4tb HDD)

I will miss the cable management from the Mac Pro I think, but I can deal. Any thoughts/suggestions at all?