Hi there,
to get your RAM running at 1600MHz you need to manually set the timings in the BIOS under the MIT section.
You will probably only notice the real benefit of the extra cores on your CPU when you are doing some intensive number crunching with it but a lot will depend on the actual software you are using and what you are actually trying to do. If you want to see faster start-up times and better overall system improvements then, from my own experience, I would say get an SSD for your primary drive, if you don't already have one.