If you want mutli-GPU setup, you dont need a 1kW PSU. The AX850 is alot even for 2 cards.
And your H70 has pretty much no impact on how well your cards are cooled. I'd say when you get your 600T, switch to the mesh side panel pictures and position a fan or two where the GPU fan intakes are since they will effectivly be obstructed once you install the cards so close to each other.
