Dude, why do you give a shit about cores or processor speed?
Are you going to use all 8 cores?
With i5 2500k, it has unlocked multipliers, meaning you could easily overclock it to over 4Ghz with no problem.
That RAM speed is a waste of money.
If the most intensive task you do is play games or use Prime95 or something to see max load temperatures, go with 1600mhz or some shit.