Yes, the Cooler Master is better than the Xigmatek.
You can use one chip of RAM but you lose 18% of memory bandwidth, there won't be a noticeable difference when gaming, but if you do a lot of photo and video editing you want dual channel.
The Gigabyte G1 Gaming is one of the fastest by about 1-3 fps, but also the largest so you have to make sure it will fit.
Zotac is cheaper but it shows, their heatsinks and fans aren't as good or as quiet as other brands, I can't usually recommend any of their products unless a person's budget demands it.
For the GTX 970, I highly recommend either the MSI Gaming G4 or the Asus Strix they have the best cooling solutions, they are whisper quiet while gaming and their fans turn off when they're below 60c to give you a totally quiet experience.