How good is a GeForce GTX 680?

It's not a question of whether the GTX680 is capable or not, it's whether it's worth the extra money over the GTX670 or even the GTX660Ti, and the answer is no. The GTX670 has a price tag roughly £100 less and the performance drop is marginal. I can't really say about the GTX660Ti but I have heard it's marginally less powerful than the 670 for £50-60 less.

the i7-2600 with 8GB ram is plenty.
 


Personally i think that depends on what 680 you plan to get. For instance i think the msi gtx 680 lightning is worth the extra money over the 670. Extra performance (provided you overclock) plus its quieter and cooler.
 


Your question is a strange one because the GTX 680 is the best card you can buy. The question is not whether it is any good, but whether you really need anything this powerful. True, there is a card called the 690 which is even more powerful, but it is not a viable option for most people.

Your 8GB Ram and i7 2600 are plenty