If you can run the 'perfect' 78F in your room, then adding CO2 is a good thing ( Your room is happy and CO2 isn't used as a band-aide fix for high temps. Co2 is the last thing to add to a room, the cost of if makes it kinda pointless for a newbie just getting his room & style rolling and set up)
But increasing temps 5-10F from the ideal 78F isn't a far stretch (can even save a bit on the elec bill)
But another thing to consider is soil vs hydro. Hydro res temps like to be _low_ (I've heard below 60F) But that also tosses out the flood-drain vs DWC. Any hydro system where the roots (even soil) get hot is a bad thing.
In hydro, pathogens will start growing causing root issues.
A flood/drain system is less likely to have as many issues (plus you can keep the res out of the grow room, keeping its temp down)