Are you all really sure about the "cooling"? The 7950 blows the hot air towards the BACK of the cards.

So in this rig all the hot air is blowing out downwards to the table and if I see right directly to the PSU. And because hot air rises I think you have the problem, that you

a) blow the hot air out
b) and that the hot air rises up again in the direction of your cards

But maybe I am wrong. At least with my 7950s the air is blowing out to the back.