1| You'd need to see if your processor is not going to bottleneck your GPU should you want to go for something like a GTX980. You could pass on the SKU for the Predator for us to learn of the processor inside it or you could download
CPU-Z and read off the processor tab to learn of your processor.
2| You're also going to need to know the PSU inside the chassis. All your components require a minimum and maximum wattage thus you should follow
this article to understand how much power your system needs. Mind you, you're going to have to add more wattage for overclocking headroom and longevity reasons.
3| If you are in the market for buying a new PSU, you can look through this
PSU tier list to choose...