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.
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.