I swear last week it was i5 (and only i7 if you really want, or video editing).
If you mean every new game at max settings, then you probably want tier 10. I went with 9 (well I based it on what it said for 9 last week), mostly for noise reduction, it looks pretty good. You really need to look at the specific games you want to play. See here:
www.systemrequirementslab.com/cyri/ Also, for online pvp, being a little bit faster than your opponent kind of approaches a plateau due to internet connection and human reaction time. I'm not much of a hardcore gamer though (no crysis, no water cooling, etc), so don't take my word for it.