The 3GB version of the GeForce GTX 1060 mid-range graphics card has fewer cores than the 6GB version (1152 versus 1280) but it is significantly more cost effective. As the fourth card based on the new Pascal architecture it not only runs games faster than previous generation Maxwell cards, but consumes less power and is quieter.
VGA coolers are the best way to cool your Graphics card when overclocking. This prevents damage to your components and can also decrease fan noise on certain graphics cards. Updated
An SLI (Scalable Link Interface) bridge is used to connect two or more NVIDIA graphics cards together for increased performance in games and applications. SLI bridges come in different sizes as the PCI-E slots are not always in the same place on motherboards, so make sure you buy the right size SLI bridge.