Palit Sonics, does that make a difference?
I had some Palit 2GB 560Tis (same cooler) in SLi, and agree on the rear exhaust but for a different reason:
When you have those dual cards stacked on a motherboard that only has two PCIE slots a 2.5 slot card with the fans in front gets the heat from the bottom card rising straight into those two fans.
It's not bad if you have three slots and can put some distance between them. I tried a 10% OC on them (in a HAF932 with a 1200 Silverstone PSU) and was crashing. They did run fine at stock speeds.
I replaced them with 3GB GTX580s, rear exxhaust, that I don't bother to overclock because they chew through everything at 57X10 anyway.