If you must go with either one of them, go for the FX60. It's multipliers are unlocked in both directions, and the FX-series always overclocks better then every other AMD (even opterons).
Your performance will not improve though, I have an X2 4400+ OC'd to 2.8GHz, and an X1900XTX (arguably faster then the 7900GTX) and I still get like 3fps at the title screen of WW. For dolphin you'd actually be better off with an FX57 since its stock clock is 2.8GHz, and Dolphin isn't coded to take advantage of SMP systems. However, no processor out today is fast enough for dolphin (SMP support would help greatly, but that's supposed to be fairly hard to program.)