Switching to 2-300 watt led w/2cooling fans on each.Im set up for HPS air circulation w/6" exhaust fan
Now that i think about it its about the same.Still any advice will be welcome.
Ventilation is for more than cooling your lights and/or space. Plants need a continual supply of fresh air for proper photosynthesis. Unless your space gets too cool, I would recommend the same air exchange as you had been using with your HPS.
Setting up CO2 is a big thing--it takes a lot more than simply throwing a CO2 tank into a space. There are really a lot of other cheaper easier ways to deal with cold.