When it comes to the i5 versus i7 and just for gaming, there is no reason whatsoever to get the i7.
That is the blanket statement you can actually make. Beyond that, any blanket statement is dangerous.
People who use an i3 with HT will find tangible gains because the two main threads can be more fully utilized for the game itself because the CPU can offload the less intensive threads (background tasks) to HT. Also, newer engines can make better use of HT, some engines run less intensive threads that can be scheduled to HT.
Like others pointed out, there are lots of users that record while gaming. At that point the i7 is no luxury, although if you use Shadowplay the i5 will suffice still, but this is proprietary for Nvidia cards. So again, no basis for saying the i5 is enough.
About the 970 and 'mid range'. The primary advantage of 970 is in newest titles at 1080p, if you look at anything before 2014, you will see the 970 has no real merit at 1080p. Look at TW3: turn off Hairworks, and I run that 'heavy game' on my mid range GTX 770 with relative ease at high settings. No urge to upgrade until you turn that performance hog 'on'. Just for a little bit of perspective right there on what is 'needed to run'...
Price wise, the 970 is not mid range but borders the high end. The fact that we have big chips now that are part of the yearly refreshes with an astronomical price tag, does not change the playing field of mid range. Mid range, to me, is still the 250 eur maximum and if ANYTHING happened to mid range territory, it is actually the other way around: getting a mid range card has become cheaper because gaming needs have not advanced all that much, evidenced by the re-re-refresh of AMD's cards. The 670 was also launched as a high end card, and the 690 was the dual gpu version of that high end card. Let's keep calling apples apples, and not change them to oranges because Nvidia and AMD have upped their pricing game and because a couple % of the gaming market likes to lead the 'master race' with a lot of fanfare about their newest acquisitions. 1440p is still not an argument in terms of being mid range, because it simply is not mid range but high end. 1080p is mid range, and for that, you only need a 970 for the newest of games at the highest settings. People on this forum sometimes forget Ultra settings have never been mid range territory, and neither has 60 fps ever been mid range. Mid range is ultra @ 30-45+ or medium/high @ 60 fps.