go for 2500k or 2550k
3xxx series cpus use cheaper metal top where it makes contact with the cooler making them run hotter so in my opinion go for the older gen since they will run cooler so its better for overclocking..i have 2550k and I have it running at 4.8ghz
clock for clock the 3570k will be faster, when i say faster for everyday use you will not even notice.
Now since your getting the k version im guessing your overclocking. The 2500k will need around .2ghz more to equal the same performance as the 3570k. The second gen cpus seem to overclock more then the third gen cpus and stay cooler as well.
If your only going to overclock with the turbo boost then i would go for the 3570k. If your wanting to do some good old fashioned overclocking the i would go for the 2500k, it stays cooler and and clocks higher.
Also If all your doing is gaming the 8gb of ram will do. You might also look into getting a SSD. Spinning up a 2tb plater will slow down game load times as well.