If you're not on a budget, my advice is the avoid AMD if possible.
I finished my new build yesterday, went from AMD setup to Intel and I gotta say, in just 1 game I tested (without v-sync, to test hardware) there is a +130fps difference on highest settings, which says enough. (from FX8350 to I7 6700k)
If you truly need a multi-tasking beast (gaming, streaming, rendering, applications, music all at once), a 5820k for instance is very good (6 core), much better than any +4 cores AMD cpu.
To answer the overclock question: yes, you can overclock non-K versions but you are limited at the multiplier (which you need to raise to overclock in BIOS/UEFI). So you can't OC as high with a unlocked (K-version) CPU from Intel.