Hey sunnyboy, good to hear about the go ahead to expand. I use two 1 meter squared tents (3' 4" x 3' 4" x 78"). I have a 600 in each. I did not buy them at the same time and my second tent is more recent. Depending on the type of growing you want to do, I would say other than doing large single run crops, I would recommend two tents. So far I've been growing perpetual by the seat of my pants and I like growing that way but I'd also like to be able to do full tent runs, and scrogs and sogs too. This gives me that flexibility. It also allows me to run the two lights on opposite shifts so your electricity draw is even, as well as lower temps not having two running at the same time. Both my tents are budget end with the newer one being somewhat better but still there are some light leaks in the stitching, and on the older one there's small holes forming where the door/flap creases all the time when opening, and when it was new, it was opened a lot. The light leaks may be what is causing some of the slight hermying that's been going on lately in my garden, but it could also be genetic too so I'm not getting all riled about it. My tents are in a room that get's utilized for other things throughout the day so the light is there but I'll be solving that when I hang a drape track around it and hang these heavy drapes, problem solved. Not sure where your thinking of putting yours so hey, if money's not too much an issue then maybe go with the higher end tents. Heat can be an issue with tents so I highly recommend access to fresh air. And for exhaust I'd go nothing less than a 6" fan per tent, or what I did was 1- 8" fan drawing from each tent through 2- 6" filters.
Many ways you can go but that's my experience, so far.
Cheers.
