I don't see any problems, but since you want to run this for 4 years I would recommend some better parts. A motherboard with another x16 slot and a higher wattage psu for crossfire in the future, and P67 or Z68 motherboard with a 2500k for future OCs. You could probably do that and still come in under $800.
don't be cheap with the psu+ get about 750w for future crossfire.
don't be cheap with the mobo and get one with 2 pci e slots that are either 16+16 or 16+8
And i highly suggest you wait till the new 7xxx gpu series comes out.
With this, you can crossfire in the future when games get more advanced.
Also, the i5 2500k is on sale as well for 205$, pick that up instead of the 2500. Spending the extra 15$ will help keep the build even more future proof.
You wont need to OC right now, obviously. But if you want to keep it future proof, you might need to in a few years. You can get a decent OC without even changing the stock voltage. IE, it's pretty easy/safe, you just need a tiny bit of knowledge and to be careful. That's why i'm suggesting the 2500k instead.