You need a power supply with a rating of 434W on the +12V rail to stay below 80% load on the power supply.
You also need two PCI-E power connectors.
A really good 450W power supply like the Seasonic G 450 would be fine (not just for two days, but permanently although running at close to capacity).
Most 450W power supplies would not be ok.
I don't know if you have ordered your new supply yet, but if not choose quality.
A good quality 550W power supply would be perfect for this build.
Seasonic G 550
Antec HCG 620