idroid :
i think the oposite.... haswell should offer about 15-25% more CPU performance than ivy.,
The Key is
Intel will be using a different transistor type(the article mention they should be more efficient= less heat) and probably go back to soldering the CPU core to IHS instead using cheap TIM. As a result Haswell should heat-up a lot less while OCing, you can probably expect Sandy Bridge level OC %(5/3.3-> 50% overclock on air instead of Ivy's 4.6/3.4-> 35% on air) and plus how many % it is better against Ivy at the same clock rate.
To me Haswell have the following things going for it:
1. Lower TDP
2. Better overclockablity (basically fixing Ivy's design/manufacture flaws and unleash Ivy's OC potential previously only seen in LN2/DICE)
3. Much more advanced iGPU, its high end iGPU is claimed to double the performance of HD4000, combined with the next iteration of Virtu MVP it can help your GPU more.(not sure about this yet)
4.Z87 Chipset: Double the amount of SATAIII Intel ports(to 4), Doulbe the amount of Intel USB3.0(4), maybe integrated Thunderbolt.
5. It should out perform Ivy per clock by a certain percentage, not sure how much yet.
Back to the OP:
Extreme 6 won't disappoint you, it is an award winner on this site after all. However I prefer ASUS P8Z77-V(not Deluxe, too expensive) or Gigabyte ud3h/ud5h because they offer more 4 pin fan headers(5/6 vs 2) and I really dislike the ASRock fan control options, just my opinion.