AMD Phenom II X2 550 vs X4 940?

[Decillion]

Paired with a HD 4890, is there a major difference between the X2 550 and the X4 940 in gaming? I'm thinking about building a new computer soon, but I can't decide on which CPU to get. I know that if you're lucky you can unlock the 2 extra cores on the X2 550. So with the 2 cores unlocked, would the performance basically be the same as the 940? What about without the 2 extra cores?

I probably won't upgrade my computer for a few years, so I'd like it to last as long as possible. I'll mainly be using it for gaming and watching movies/TV. Right now I'm leaning towards the X2 550 since it can be had for $80 shipped (thanks Bing Cashback!). But if its worth it, I can probably pay the extra money for the X4 940.

Thanks

[fishstix]

The performance probably wont be the same if the cores are unlocked. I imagine you won't tell the difference in games unless you benchmark though. I bought the x4 940, even though I know I probably wont be using it to the fullest. I have rendered video while gaming before once and it didn't lag xD