Maybe im seeing the specs wrong.... but i believe it says Phenom, not Phenom II, and a stock Phenom II x4 850 is clocked at 3.3ghz not 2.5ghz, i think you got the wrong cpu name. and none of the CPUs listed here can be used with your motherboard.
You're right. I looked back at the specs, and indeed, the board only supports the Phenom, not the Phenom II.
In this case, I change my opinion, and I think a MB, CPU, and memory upgrade are in order. There is no sense in getting another Phenom CPU.