I have a 5770 and a 5750. I had the 5750 first so it is the card on top. Is there any reason to switch the cards so the 5770 is on top. The 5750 obviously gets hotter with full load aobut 79-82 C. The 5770 on the bottom rarely breaks 60 C.
More aboutwhich card crossfire
cfx defaults back to the lowest settings...so it wont affect that........
id just put the cooler running of the two in the primary slot