Before this starts getting really out of hand. I'll weigh in.
While I do believe (based on my own experience with 1080p gaming), in Skyrim, Battlefield 3, BattlefieldPlay4Free, among others. And maher, I play at ULTRA settings, not medium/high. The Phenom II is still a perfectly viable gaming CPU. That being said, PileDriver 6300 is a worthy successor to P II x4s. Those who already have Phenom IIs (like myself) would see no real improvement from buying one, but for first time buyers looking for something on a tight budget, the 6300 deserves a look.
As mentioned, 5-6 years is asking a lot from ANY computer, be it an i5 or a FX-6300 for gaming. I've got an old Dell XPS laptop with a Core2Duo w/ Nvidia 8600M. It was a pretty ballsy laptop when it was brand new, 5 years ago. Now? Still great for browsing, doing homework on, and although I quit months ago, it would still play Runescape at best possible settings. But its not the "gaming computer" it once was.
If you plan on playing the same games, of course, it will last you.. well forever. But if you're constantly upgrading your game library with the latest titles and expecting to max them, you're going to be disappointed. This is just a sad fact about computers. Which is another reason to find a good balance of components that meet your needs today. Not overbuying on parts and trying to "future proof" them. Its more financially sound to buy a cheaper system that can meet your needs now, and scrap and rebuild in a couple years.
And yes, the only difference between AMD 970 and 990 chipset is the PCI-E lanes. Beneficial if running a crossfire/sli configuration, but offers nothing for a single card. And single card systems are almost always the better option.