my grow room is 16ft long 9ft wide 8ft height but it's a 2in1 grow room so it has a veg room and a flower room together

to tell you the the truth i don't know much about tents but a friend of mine is doing a 600hps in a 4x4x6 tent it looks like he is running out of space his shit is growing too big too fast so if i was you i would do some research see what kind of plants your doing make sure you veg them the right height before flowering cause they tend to double in size or add 6inche during flower cause u only have 6.5ft thats not a lot of light space to adjust, so 600 i think is good for the tent but u might have to get a good ventilation system