Power supply for a 6x GTX 1080Ti 2x GTX 1070 rig

Hi,

Considering changing the plan and going with 6 GTX 1080Ti's and 2 GTX 1070's (instead of 8 GTX 1070's) for a build I'm working on (due to the price increase on GTX 1070's). The reason for the 2 1070's is I got them before the price increase on 1070's.

Now, this is going to need a lot of power obviously. From what I understand, GTX 1080Ti's should draw around 250W unless I overvolt them (or set the power limit above 100%), and the 1070's should draw around 150W. So that's 1800W in total plus let's say an extra 200W for the motherboard/CPU/fans etc (will be using an M.2 sata SSD). If we split this up to be supplied by two power supplies, let's say...

PSU1:
4x GTX 1080Ti @ 250W ea
Total: 1000W

PSU2:
2x GTX 1080Ti @ 250W ea
2x GTX 1070 @ 150W ea
Misc (Motherboard/CPU etc.) 200W
Total: 1000W

Now, clearly you don't want to actually go with 2x 1000W PSU's in this case, but how overboard should I go? Would 2x 1250W PSU's be enough or should I go for 1500/1600W PSU's (there doesn't seem to be much inbetween). In Australia there isn't really as much variety to choose from as what you can probably access in the US.

These are the PSU's I'm considering (keep in mind $AUD). Just not really sure how overboard I should be going. At stock clocks and 100% power limiter, the reference GTX 1080Ti draws 250W correct? In an ideal scenario, would I want the card drawing more than 250W?

eVGA 220-P2-1200-X4 SuperNovo 1200W Platium 80+ - $355.00

Seasonic 1250W 80Plus Gold Full Modular - $335.00

eVGA 120-G2-1600-X4 SuperNova 1600W G2 80 Gold High Efficiency - $489.00

Corsair CMPSU-AX1500i 1500W ATX Power Supply, 80PLUS Titanium - $579.00