There is no "perfect" temp, but I know for sure you do not want over 78' if not using a Co2 system.

If just using passive ventalation then I would make sure you are around 74, but this varies depending on the grower. I know alot like it 70-74 because bugs and such are much less prone to attack. They thrive at 76+.

The first and for most, thing is that you make sure you can hold your hand , at the upper most point of your plant for 60 seconds and feel totally comfortable, maybe a slight tingle but no burning. If your hand feels hot then your plants " feel " hot.