If you plan to now tweak your Neptune cubes (changes the voltages/MHz per chip) then yes you could get away with 1300 watt PSU's to be safe. I know EVGA is having a sale on their SuperNova 1300w G2 (4th Gen) PSU's, they cost $195 CAD each. I picked up a couple for a friend.You will have to buy the 16AWG cables about $10 each plus shipping.

I wish there was someone making and or selling (in stock) in the Greater Toronto Area so I wouldn't have to buy them overseas.