its hard to say
8'x5' can do a bit over 160 plants i believe, no?(if its one complete table) that's alot of mouths to feed lol
with that said instead of optimizing the potential lighting to the size of the grow,
rather optimize it towards the type of grow u wanna do.
3 1000's would be less efficient imo, considering the type of the setup (s.o.g). 1000's can penetrate foliage deeper than a 600 and technically pump out more lumens but considering you cant have them as close as 600 you will never utilize all those lumens,
with 600's you also get more lumens per watt making them more efficient,which leads me the phrase less is more lol
the only upside in the 1000w scenario would be less total wattage
3x1000w=3000w = 435, 000 lumens total
6x600w=3600w = 540,000 lumens total
400w HPS: 50K lumens (125 lumens per watt)
600W HPS:90K lumens (150 lumens per watt)
1000W HPS: 145K lumens (145 lumens per watt.)
getting easier to see the better choice eh lol
6, 600 watt'ers would be the way to go, no they don't penetrate as deep but thats not as important in s.o.g as your only growing the tops, the total lumen output to the plants is more important. also you can drop your lights closer in-turn letting your plants receive more lumens. heat may be an issue though.. but as long as you get cool tubes with strong enough exhaust for your lights you'll be fine. apparently cool tubes are the best, even better than air cooled hoods.
hope this will help you decide
(keep checking in on my link ill be starting my grow soon, and probably start a grow journal as well..
later days