I think there should be a little more clarification here. Power phases are important for overclocking but so is cooling. Typically the more power phases once can achieve a cooler, higher clock and more stable overclock. However, that doesn't mean it's impossible or bad to overclock with less phases. Will it be a little more difficult to reach higher clocks, yes. But you also need to decide how much overclocking you want to do. If you're only planning on a mild overclock, sub 4.4 GHz, you could get that done with a 4 phase motherboard. For higher clocks, you will definitely want to get a board with more phases.
Cooling is also important. Good air flow in the case paired with a good CPU cooler are key for stable builds too. While most people are concerned with CPU temperature, keeping the VRMs cool is important too.
There's also a cost/return aspect. Overclocking to many isn't necessary any more because of the low returns in certain areas. Overclocking will help but to what extent, you'll have to decide that yourself. For CPU benching (processor related tasks like compression), overclocking will help. In gaming, that's a hit or miss (mostly a miss).
http://www.anandtech.com/show/8227/devils-canyon-review-intel-core-i7-4790k-and-i5-4690k/5
This is why it's more of a hobby now. The main reason to consider overclocking is to retain longevity. Intel's current path has very small gains over each generation. Meaning, a small overclock can but one at a newer generation's level.
I'm not saying not to buy the 4690k and not to overclock, I'm simply providing information about what to expect.
Edit: I also forgot about the CPU lottery. Each chip is different. Just because someone can overclock to 4.7 GHz, doesn't mean you'll be able to. Each chip has a different ceiling.
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