Here is a great Tom's article on the subject, it's from the summer but still very accurate. At the bottom of the article you can see a handy list of all the best price/ performance CPU's:
If you can afford it I highly recommend the Intel Core i5-4590, it is a much better performer and will last quite a bit longer than the Intel Core i3-4170. If you can afford it the next best step up from there would be the Intel Core i5-4690K.