In June Intel released its new Kaby Lake-X desktop processors. The cheapest Core i5-7640X might have sold in the $270 range when it first launched it's now down to $224 after coupon at Jet. Be sure your motherboard can handle this processor before buying.

I think most PC builders will be happy enough with the Core i7-7700K processor, but going with a Core i7-7740X will get you a slight boost in speed and now for $307 at Jet instead of the $350 list price. Best price online, just be sure to use an X299 motherboard which is going to be a bit more expensive than the Z720 MOBO for its competition i7-7700K. That said, at $307 the i7-7740X is cheaper than most retailers charge for the i7-7700K.