The 6300 is the bang for the buck CPU of the moment. Reviews show it easily overclocking to a point where it can match the i5 3570.
Sure the 3570 if its a K series chip can OC as well, however you shouldn't really need much more performance that a stock 3570 for a few years anyway. Plus you have 2 extra cores for any trans coding work you might want to do. Its a pretty sweet balance right now.