You are paying for the higher default clockspeed and the convenience of being able to OC by just upping the multiplier. Takes memory, bus speeds and ht speeds out of the equation. Plus you are more likely to get a higher OC out of the 955 with the right board.
I will buy 925 and OC to 3.2 GHz.
Btw. What MBO should i choose Asrock M3A770DE or 770 Extreme3?
It's a matter of taste. Extreme3 is a bit better but also a bit more expensive.
The biggest differencies are :
Extreme3 supprts up to 6 cores, M3A770DE only 4
Extreme3 supprts SATA600, M3A770DE only SATA300
Extreme3 supprts has Realtek ALC892 audio, M3A770DE only VIA VT1708S
However Extreme3 has only 1 PCIexpress 2.0 x 16 slot. M3A770DE has 2, running X16 and X4 mode respectively.
So it basically is a matter of which components you're going to use.