That sounds like a great deal. Yes, the more the better but remember the more heat you will have to deal with as well. Weigh that factor in as you may have to buy a ventilation fan if you can't keep temps around 85 with the lights on.

What I would do is get the 600 and then leave two sides of your table open with a couple of normal oscillating fans blowing on the plants. Are you able to leave a door to the 12x12 room open? You may get enough ventilation this way but like I said if temps get too high you will have to get a fan or else growth will stop.

Don't know much about Haze except that usually haze is sativa and takes a long time to finish (like 12 weeks) and will get very tall. Plan accordingly.