What size light should i use?

I have a 76x76x76 grow tent, I am going to do a perpetual grow with autoflowers, Would a 600w hps be enough for this size tent?

ok, so its 6x6x6 ft. Yes, 600 watt would be ok.... but if it were me, and you can vent the hood, and heat wont be an issue, I would go with a 750 or ideally a 1000 watt. But you could even use a 400 watt depends on what ur trying to do

You will want 2 600's in there

I was aiming for a 600w cool tube, would it effectively light such a room and its 6.5x6.5x6.5 feet

The tube will effect the brightness, so you may want a 1000 watter then.