Which mobo for Matrix 7970 Platinum in Crossfire.

Help,

I'm trying to find a motherboard which will allow me to run my two Matrix 7970 Platinum cards in Crossfire.
I considered the Maximus V Extreme but if use the recommended slots of 1 and 2b the cards are very tight together with no room for cooling the first card. If I move the second card to slot 3 will that give me performance issues ?
I'm looking for a motherboard that will give me proper speed and a decent space between the cards.
I have a 3770k CPU on LGA 1155 Z77. I only want to use air cooling.price doesn't concern me.

Have a great New Year