taha2001 :
is asus z87-a a good mobo for i5 4670k??
It's as fast you'll get them, but it depends on the features you want. I have that motherboard and I'm totally happy with it. If you can't see anything wrong with it, definitely buy it.
As for the whole IB vs Haswell, be wary of the silicon lottery and IHS lottery. On average a IB may overclock higher, but it may not. I have a 4670k and it goes to 4.5GHZ at 1.265V. Which is pretty sweet. Not extraordinary, but it's on the stock cooler (I don't run it like that, obviously) so I'm sure it'd go at least 100MHz higher than that, probably even to 4.7GHz if I had a decent cooler on it.
Of course, it's all a lottery. The differences are so tiny anyway, you won't see any improvement 99% of the...