Hey mate I'm from aus too
Looks like a decent build, the future plans look good too, i guess you can push your SATA SSD to a secondary drive when you move to the m.2 drive....personally though, after working with an m.2 drive in my yoga900s, I'd want it straight away in the new build, because the difference it makes in overall system snappiness, program loading and virtual machine resuming and booting is very noticeable.
I think I'd go the 1080, mainly because of what tech costs for us here in Aus, might be worth the extra 150 upfront to get extra time out of the build before upgrading in a couple years time.
I also reckon you could get away with an 850 evo and save a few dollars, I have an 840 evo 250gb, 840 pro 500gb and 850 pro 500gb and really there is not a huge deal of difference between them in terms of extended use and performance. (They've all served as an OS drive at some point, now just the 850 pro is an os drive)
The 750watt is excessive, but I don't see that as a bad thing in power supplies, having an extra 20-30+% headroom on your psu is a good thing for various reasons. I guess if you could get a 650watt with better quality internals and more consistent power.... i'd ask @TwoCables about that one