To answer all your question. Best is to google it. But i will digest everything.
An i5 and i7. This 2 differences are mainly the slight base clock speed, cache memory and hyper threading capabilities.
Similarities are that they are both quad cores CPU.
However in terms of gaming, this 2 CPU offers very negligible performance differences. There is not much gains in performance if you gonna spend the extra $1XX more for an i7. In gaming, the main horsepower is the GPU. Spend more on a GPU rather than a CPU.
Theres pros and cons on the r9 290x provided. Pros is that this card is on promo, and also one of the best AMD graphics card ever made. But however, in the expense of high heat output and high power consumption. But if i were to go for R9 290x, i would go for MSI r9 290x Gaming Edition instead. Reason being, it has a proper backplate support, and also a much quieter cooler and comes with a 3 years warranty. And going for $449 or less in SLS now. Too bad you have missed the r9 290x Lightning edition. But if there is in SLS please grab it. Its one of the best r9 290x custom made by MSI.
On the other hand GTX970 is a much more cooler and much lesser power consumption card. Its temp never breached 70deg (on major brands cooler) other than r9 290x going over 84deg. Performance is slightly tiny bit behind r9 290x in certain games. But however its a bit pricely if you going for major brands such as ASUS MSI and Gigabyte.
MSI GTX970 is a bit pricey. But however you get what you paid for.
1. All new Twin Frozr 5 technology cooler. Its quiet at 100% fan load, it brings in more air with their new large Torx Fan blade.
2. It has soldered SuperPipe configs. The S Shape Heatpipe drawing the most amount of heat out and away from the GPU core. The U shape works on the lesser heat area of the GPU core transferring to the outer portion of the heatsink.
3. With SuperPipe configs, its cooler than lesser known brands. Not just that, Twin Frozr 5 fans wont turn on till it reaches 50degs and above. This allows your fan to so call technically speaking "last longer".
Fractal r5 is a very clean and unique look case. Its one of the best chassis i ever worked with. But theres always a problem in minimal looks chassis. They usually have bad airflow as their front always blocks out air intake.
Powerline. Its different from direct wifi. This allows you to have a 3 pin plug with wireless features connecting to your router, and use in conjunction with a RJ45 cable out to your desktop. I wouldnt say its more reliable than wifi. Cause its technically still wifi, and worse is that it increases your ping rate. Only use a PWL if there is a super weak signal across the desktop and router. Using this PWL at a certain line of sight with your router and using the RJ45 cable to your desktop will work properly.