4GB (Saphire Nitro+). Use Claymore miner, it can mine some DCR without affecting ETH rates (i have similar on my 480 on windows but there i overclock) . Also i found with geth my cpu usage was high (on both linux and windows it seemed to chew up 1/2 core per gpu. so 4 gpus kept my 2 core cpu at nearly 100% until i switched miners. (with Claymore it went down to 5%. ).