You didnt say what you consider to be a lot of herb
What did you get from your last grow?
You ought to be able to get 250gms from your 600W hps without doing anything special like pruning or scrogging.
Yeah dont run at full capacity. You have no flexibility, no room to manouver and everything is a PITA. I would try 6 or 7 5ga pots and see from there
Some things to do to increase yield without scrog or magic juju juices.
You can improve your yield a lot just by getting the basic cultivation right. Giving her everything she needs when she needs it (to quote prof Marijuana) and not stressing her. It helps if you grow the same strain over.
Start from clones.
Pick high yielding strains.
Canopy & light management. Use pruning/topping and LST to get a nice even canopy.
Adding a seperate veg cab will dramatically increase your output. You dont need much space and a 250w light or cfls works fine. Your tent will be permanently on 12/12 and every time you harvest a plant you pop a fresh one in from the veg cab. This way you can run a full harvest about every 2 months instead of about 3. A 50% jump in productivity.
Add more light. Cfls placed to shine on the sides of the plant and lower regions which dont get much light.