Temps will probably be OK; try and put a thermometer in there when you get the light.

Yes, if you get the 600, it will pay for itself on the first crop. You will definately not be sorry.

About the haze, like I said I have no experience with the strain. You'll just have to play it by ear. You can prune them just not after triggering flowering and make sure to give them a couple of weeks to recover a bit.

What I would do:

Grow seedlings under flourescents (keep flourescents 2-3 inches away from tops w/ airflow in between) until you setup the HPS. Veg under the HPS till they are 14-18 inches tall (measure from soil to top), topping (pinch off the main growing tip) when they are 12 inches. This should take 6-8 weeks. Then flip to 12/12. Flower for however long it takes. They will stretch to at least twice their height so you may have to take the table out. Make sure you have a way to raise and lower the light. Chain and s type hooks work well.