Yes, it'll run SCII just fine.
To explain unlocking, I have to explain how processors get their clock speed. I'll use the current AMD setup for example since I know it from memory, but Intel is much the same.
You start with the base clock frequency of the north bridge, which is the interface between the processor and the rest of the motherboard. On AMD systems this is always 200MHz. However, the CPU has a "multiplier" in it that does just what it sounds like. The Phenom II 955 has a multiplier of 16. Thus, 16 x 200Mhz = 3.2GHz, the 955's clock speed. In most setups, you have to change the base frequency to overclock. Doing so also overclocks the RAM, so both the mobo and the RAM can be a limiting factor. However on an unlocked processor, you can change that multiplier. Bumping the 955's multiplier up by one point yields 3.4GHz, the same as the 965, which is amusing, I think.
That's not the whole story though, because if you overclock your cpu by only using the multiplier, then you don't get any RAM speed increase, so what most people do is mix the two. You generally get a better result than by just using the nb.
However, that 950 should overclock just fine. People regularly get them to 4GHz or more.
As for the mobo, you said it was $40 cheaper? Very strange...x58 motherboards are usually significantly more expensive. Which one is it?