MSI, Zotac and EVGA are reputed brads in graphics cards. so which one of them is the best?
well... there are a few points that you need to take care of when buying your unit.
1) clock speeds: clock speed is responsible for faster memory operations or simply the frequency your CUDA cores operates. the faster are clock rates the faster you graphics card is. but it does affect a little FPS in games and not hugely affect your experience in low-med-high settings in games. so, there's nothing much tow worry about.
2) power: the power demand of each manufactures's model is different, no matter if you get a 6 pin or pne without any power connector it will not make a difference in games.
3) looks: no! looks does not effect performance in any way! the dual fan design is just for more cooling potential, it just helps cooling card better during load or heavy gaming sessions.
My advise is to go for the zotac model, it has overclocking potential, it does not have a power connector so you don't need to worry about PSU. msi and evga are good but not as feature packed and suitable for your rig.
Thanks for reading my answer, hope it helps (sorry for my bad english)