Id stick with your 2 600s, add a bare bulb mh in the center if u can.
I noticed in your sketch u asked a question about your dehumidifer; it must be in your flower rooms or your humidity will be too high, if your fans do their job, it shouldn't have to run much at all, more when the lights are off than on.
If you have the room, your going to what to put a Y exhaust on the end of your exhaust/carbon filter. Put a temperature controlled damper on both side of the y. Your going to need the dampers to be opposite of each other (one open, one shut). Put the open side on the end of the y that would be your exhaust. This is going to allow you to run your carbon filter as just a scrubber when your room does not need to bring in fresh air (it's already too cold in your room), and to run it as an exhaust when it is needed. Buy a 75 dollar day/night controller and plug both dampers into that. Set your day(max) and your night(min). Gives you way more control on cold temps in the winter. Obviously it doesn't help cool the room if it gets too hot. But can save u a lot of money on power bill in winter.
Personally, id get a 12k btu mini split, 100 pint dehumidifier and a fuzzy logic co2 controller/tank and not have to worry about a single thing. 100% control. Small window ac for drying area, can be converted to portable if your in a basement.