before buying the upgrade parts, take care in ensuring that your mobo will support the 970BE. you mobo's web page may say that phenom II x4 cpu's are supported but you must specifically check how much TDP and which CPU steppings are supported. For instance, a 125W TDP support mobo might support a 965 BE c3 stepping 125W cpu but not a 965 BE c2 stepping 140W cpu (yes there are several cpu's which have the same name and frequency but differ in TDP and revision/stepping).
Make sure you do not end up going through the hassle of returning the cpu and then locating one that your mobo can handle.
Upgrading to a 7770 will require you to buy a psu which has a 6-pin pcie power connector. A 500 W psu from Corsair or Seasonic or PC Power & Cooling will be good.
6pin PCIE: http://techreport.com/r.x/psus-0907/pcie-connectors.jpg
In case you can't buy a psu with a pcie 6 pin connector, you can buy a molex to pcie connector.
Molex to PCIE: http://imgs.inkfrog.com/pix/fengshan/______6pin___4pin.jpg