All Athlon II and PhenomII is on discontinue Pharse... Replace will be APU and FX Series..
but if you already have GA-970A-D3 you better use FX Chip
for you price range is FX-4100 $109 or FX-6100 $149
Benchmark reference FX-4100 VS FX-6100 VS 960T => 4024 VS 5582 VS 3764
CPU Support for your board http://www.gigabyte.com/support-downloads/cpu-support-popup.aspx?pid=3908
DONT get a 4100 they are truly bad I have one on my HTPC. My Gaming Rig I'm on now outperforms it in everyway and the only real difference is this uses an unlocked 960T (6 cores @ 3.8GHZ) and the other uses the FX4100 (Snoozedozer), Heck the 960T at stock outperformed the Dozer build. Buying the 4100 was the biggest mistake i have made lately i should have gone with another 960T or done the Intel route. (Luckily the wife is the main user and she is impressed with games set to LOW
For your Board and around the budget of the old Athlon, the 960T is best thing about thats still readily available