I think by ATX it is the best to pull the hot air out of the Case.

I think do you push the air in, so the hot air from the Graca, or the Prozessor, can be moving over other parts of the board and maybe in some corners, the hot Air will be catch.
So this Parts are getting hotter and hotter.

But with the new BTX? System Architecture is its still possible to blow the Air in the Case. There are some Heatpipes which will work in this way, and the Airstream is in the new System is better.

Das Ganze ist mehr als die Summe seiner Teile(Aristoteles)
Aber wenn man das einzelne nicht mehr beachtet, hat das ganze keinen Sinn mehr (Stone)