Should I Upgrade From 600w To 1000w?

Should I do it? If I get an average of 75 grams per plant, what would I get with a 1000?

Try it and see, nobody can predict.

your yield will go up if all things are equal. Penetration down increases by approx a foot by going to the 1k.
you'll be happy.
but to blow the roof off, two 600w combined for 1200w gives you way more lumens and results with only 200w more power.

It sounds like you are looking to increase yields? If that is the goal I would double up, and add another 600, if the space is there. Either way it should be fun.

I've decided to go for the 600w, setting up one of my friends.

My 1000 watt grows kick my buddys 600 watt grows by almost double in yeild. My 27 day old plants are bigger then his 60 day old plants.