I have: Antec 900, Freezer 7 Pro, Asus p5Q-e board, Q6600.
The 900 has very good air flow and with the back fan and the top 200 in such close proximity to the pcu it dosen't matter which way you place the freezer 7 pro.
I placed mine facing up toward the top fan. By doing it this way the 7 pro pulls air right through the northbridge heatsinks there-by keeping a notoriously hot chip cooler. Also the ram dosn't interfere with input airflow. The back fan will keep the voltage converters plenty cool.
Everything in my rig is kept very cool.
At idol my q6600 is at 20C and running prime 95 full bore cpu temp is 32C. The cores run 39-40 C peak.
I use Arctic Cooling MX2 thermal paste. It's the best paste out there at this time. non curing, non-capactive (a biggie!!)
The freezer 7 pro comes with MX2 pre applied so a plus for us and no worries.
The fans on my 900 are set on slow also. Cool Quiet and speedy!