So your closet is 30 inches wide by six feet long by five feet tall. The good news is that I have grown in a similar closet; the bad news is that a five foot ceiling doesn't give you much vertical space. The best HID lighting for that space is either a pair of 600 watt lights in a long glass tube, like you described, or a 1,000 watt light on a mover. I personally prefer the 1,000 watt on a mover, and I suggest you get a high-end mover that pauses at each end. This will give you more even growth and stronger plants. Heat is another issue, and the pair of 600 watt lights in a cool tube might be the better option if high temperatures are a problem. If you can keep it in the upper 70s with a light mover, go with the 1,000 watt light.
Digital ballasts are a great option, and they have continued to improve in recent years. For two 600 watt lights, I prefer two ballasts over one dual ballast. A dual ballast doesn't save any electricity; it is simply one enclosure with two ballasts inside. If one of the internal ballasts fails, you'll have to shut down both lights for repair or replacement. If you go with that option, I recommend keeping a spare magnetic ballast for emergencies. If you get a 1,000 watt light, you might want to start with a digital ballast and buy a spare magnetic when you can. Then you will be able to use a top-notch ballast with a low-cost backup ballast in case of lighting failure.

Regarding retail stores and organic nutrients, you will need to do some legwork. There are tons of great stores in your area, so start shopping around. Find a knowledgeable sales clerk who grows with organics. You can build a friendly relationship and exchange information each time you stop in. This type of interaction will give you access to expertise and troubleshooting, but you must find a reliable source with a deep understanding of organic plant science. If he or she doesn't know much about beneficial bacteria and fungi, you've got the wrong clerk.

One more thing: keep your plants short! With a five foot ceiling, your plants will need to finish at about 2.5 feet or shorter. Start flowering them at about eight inches, keeping night temperatures above 65°F and day temperatures below 80°F. Give them B vitamins and carbohydrates along with low nitrogen base nutrients. These suggestions are key to growing short, stout plants with excellent quality.

Dread Out,
Casey Jones Fraser