I am upgrading my old Phenom II X6 1055T (running stock clocks) to a new Core i5 3570 (I did not get the "k" version because it was $30 more, and I dont intend to OC). I obviously upgraded the mobo and I also picked up a new XFX 7970 Black Edition, which is the main reason I decided to upgrade my CPU. I was worried about bottle-necking the GPU. I use the computer mostly for gaming (FPS games) I am also a graphic designer, so I also use Photoshop, Illustrator, Flash, Dreamweaver, etc. quite often.
So was my upgrade justified or should I have waited? I just ordered it today so its not too late to return everything.
More about :intel core 3570 upgrade good buy worth
The two key advantages of the 3570K over the 3570 are that the former has an unlocked multiplier for O/Cing and superior integrated graphics. Since you're planning to run at stock speed with a discrete graphics card, both advantages are moot in your case. Neither chip is a "bottleneck" for any current graphics card, so don't worry about that either.
In short, rest assured that you made the right choice and saved a few bucks in doing so!
Since I can currently get the 3570 for just $10 more than the 8350 http://www.newegg.com/Product/Product.aspx?Item=N82E168... I think I will just stick with the i5. I would probably not notice much difference while gaming, but in everyday use I think the better value lies with the i5 setup. I think it will be a safe bet to handle the next 3 years or so of productivity and PC gaming.