Microcenter has the 6600k for $199
You could save $30 off a motherboard if you buy both CPU and MB at Microcenter, and I think the Pro4 is a bit more reliable than the Pro4s.
Stick with the 8gb of RAM if it's good quality, as in you'd be ok buying a second stick of it and using it for 16gb. Don't buy 16gb of trash ram (low speed, no heat spreader) just for the size. You can expand later.