blackskull6 :
just as the title says, please explain
I think you should go with the 4670k with a z97 motherboard if you are overclocking. If not going for high overclocks, you can do z87 just fine (I have heard z97 is better for overclocking, trusted reviewers keep talking about it). The thing about the 4x90k new cpus, is that they are overpriced. From places i have seen it, ever single refresh is a good 10-20% more expensive(depends on what cpu) than its haswell equivalent.
If price is a factor - go 4670k, if overclocking go with 4670k and z97
If price is not a factor - go 4690k, and this time you will need z97 as the z87 series does not support refresh yet.