I would suggest getting yourself an Agromax tent from HTG and spend the money you save on your other gear. Secret Jardin tents are sweet. Gorilla tents are sweet. Both will cost you a ton more than an Agromax. I am not saying these are top of the line by any means, they are a great starter tent. They have tons of vents, windows, removable floors and decent zippers/flaps.
As others have said, 600 is fine for a 4x4 tent. A 4x4 space can not utilize the 1000w beam from just the way it is cast alone. Let's not get into the added heat during the summer months that in some grows, can make a HUGE difference.
You should be thinking more along the lines of a 6" fan and ducting/ports, 8" is overkill for your setup.