The x3 rana because:
-Most games don't use more than 3 cores right now
-For the price, it cannot be beaten
-Right now, it's all you need
The athlon IIx4 is really good. you won't miss much for the 0.1GHz speed difference and it will perform better in better threaded games.
The old 9850 has nothing wrong with it but it simply cannot keep up with the athlon II x4. It has more cache, but it won't make up for the lack in clockspeed, in gaming:http://www.anandtech.com/bench/Product/112?vs=29