[Build Help] 2x Tri slot or mix brands?

What would be better, pairing an ASUS 580 GTX 3 slot with another ASUS 580 GTX 3 slot in 6 slots with 0 slots of space in between? Or Pairing an ASUS 580 GTX tri slot with an EVGA 580 dual slot, allowing a single slot of space between for airflow. Would the no space in between even be viable? I ask because I need to SLI to use 3 monitors.

Specs: i7 2600k w/ Hyper212+ heatsink

Silverstone FT02 Case

8GB Kingston RAM

2x 1TB HDD

ASUS 580 GTX DCII Tri slot

ASUS P8Z68 Deluxe mobo

64GB Crucial M4 SSD

850W Corsair Modular PSU 80+

3x 1920x1080 monitors 24'