While this is assuredly very effective at cooling the area between the blowholes, it may create boundary conditions that actually impede the airflow through the case around that area. Try running both those blowholes as intakes, maybe even at half voltage. You may see your cards stay just as cool, and your overall case temperature drop. It depends on your needs, but I don't think any of us are too concerned about moderating temperature change rates. So we want surface area, and the more the better.
Turbulence can help, but only to a point.
In our heatsinks, turbulence still improves the effectiveness of the heat transfer. We want turbulence in the airflow to help the air carry away more heat. But we don't want so much turbulence that we reduce the total airflow through the 'sink. HP for instance, had a cast and machined heatsink, which featured tall, thin vanes, in the usual long straight rows. However, the vanes weren't completely straight.