Kept Brook Trout and Brown trout in 72 degree water without any issues. The catch was that I needed lots of water movement and high oxygen levels. And they were farm raised as well.
Lost the first Brook trout after the filter died, lost the Brown to the second Brook, and lost the second Brook I had kept to a Green Sunfish that gained back its dominance in the tank.
With that said, I recommend a species only tank if you managed to pull it off.
Link to my thread -
http://www.monsterfishkeepers.com/forums/showthread.php?436757-Back-with-more-Trout
At a younger age, I did keep them at 65 degrees, just to stay on the safer side until he grew used to the aquarium settings. This was also easier being in a 20-Gallon grow-out vs. a 55-Gallon.