The 8320 is basically a 8350 but with a lower clock, that is all.
You are able to overclock the 8320 pretty well, only you can get a slightly higher clock rate with the 8350. That is all, so if money is the factor then just go for the 8320 and get an aftermarket cooler for 30 dollars and overclock that bad boy even higher!
And I'm assuming you're talking about an ASRock 970 then its fine,
I have the 970 Extreme 3, that works fine with the Piledriver series, just make sure you flash it to the latest BIOS and everything will be fine.