If you got some time to read, I explain in this thread. There is more on page 2 as well.
http://www.techist.com/forums/f76/your-cpu-modern-games-guide-those-building-261626/
To put it here, I'll start out with, Passmark is a BS benchmark (coming from a reviewer), and synthetic benchmarks don't indicate any real world performance let alone gaming. That being said, HT is absolutely pointless for gaming as games don't utilize virtual threads. In some games HT can even hamper performance.
The stock heatsinks do suck, but for stock clocks they are perfectly fine as long as your ambient temps aren't ridiculously high. Most people tend to forget that i7s run warm due to having HT, and the newer Haswell chips have some of the VRM circuitry built in which also adds to the heat. Though, for warranty purposes, and the fact that you said you won't overclock there isn't a need for aftermarket unless you start seeing your CPU hit 80+C at full load.
Now, it's perfectly ok to not believe me, so I went ahead and grabbed some reviews I trust. As you can see, most games are a small variable difference and some can be up to 8FPS. Not worth the 100 extra bucks at all.
http://www.techist.com/forums/f76/your-cpu-modern-games-guide-those-building-261626/
AnandTech | The Haswell Review: Intel Core i7-4770K & i5-4670K Tested (bottom, unfortunately no 4670k)
Intel Core i5-4670K Gaming Performance | bit-tech.net
Core i7 4770K processor review - Game performance - Far Cry 2 | Crysis 2
Just giving you an idea, and to see how they compare against the 6 core i7s too (like mine), as well as AMD counterparts. For the record, I leave HT off on my rig. I won't steer you in the direction of lag, and I don't tell anybody to get an i7 unless it's necessary. The 4670k is even perfectly fine for moderate video editing, Photoshop, rendering, ect. I only tell people who use those programs on a daily basis to go i7.