Overclocking the RAM? no it is really isnt worth it to pay for faster RAM. Now as far as the processor goes in a lot of case you can see a good performance improvement for something like gaming or video editing. You can step down to the ASRock Z77 Pro4 is about as low as you will want to go.
Now if you are not going to overclock or use the IGP (Integrated Graphics on Processor) than you can go with the Intel® Core™ i5-3570 and the boards you listed above.