I ended up going with the Sapphire Dual-X 270X 4Gb.
It is AMAZING.
My 520W PSU easily supplies it, even when overclocking, a lot of games use over 3Gb of VRAM such as Battlefield 4 and Titanfall according to GPU-Z (which it can max), so I'm happy I went with a 4Gb card.
I was stupid to worry about the Sapphire Toxic having higher clocks, I demolished the Toxic's clocks with the Dual-X on the stock voltage, and then I got it up to 1200MHz overvolted.