Autos or Photos?

[Hushpuppy]

If you don't have the space for the use of T5 bulbs, there are fixtures that use the PL55 floro bulbs. These work quite good for vegging and they are half the size of a T5 for the same lumen output. They basically take a 4' T5 and bend it around into a U shape so that you still get the lumen output of the longer bulb but in half the length.

The fixture you get for the HIDs is most often universal for the different wattage systems, so the same reflector fixture will work for a 400-1000w bulb/ballast, and either MH or HPS. For vegging, I also recommend using the floros(T5) over the MH bulbs because the spectrum of the light is key to what the plant is doing. A bulb that puts out the spectrum of 6500k seems to produce the best results for veg growth.

Typically, the MH bulb puts out around 5000k spectrum, which is not as good or efficient for vegging plants because that has too much green light in it which plants don't use. However, recently I have found some MH bulbs that are being made to produce the 6500k light. If you don't have the money to buy the T5 or Pl55, then if you get the MH bulb that produces the 6500k light, you will be able to use just the one 600w light for both veg and flower.

Here is where I buy all of my lights and have had very good service with these: hxxp://www.hpsgrowlightstore.com/hps1510/best-grow-light-systems/600-watt-grow-light-sets/ipower-grow-light-600w-hps-mh-dimmable-6-cool-tube-xl-set.html
I highly recommend getting this particular fixture as it has worked very well for me

 

[The Hemp Goddess]

I have one of the PPL lights like Hush mentioned and like it. However it would take a 4 tube to give you 20,000 lumens and that still would be a bit short, but workable.

However in your case, since you appear to be leaning toward a 600W dimmable you may want to run the MH for vegging, especially since you can probably use the extra heat (another advantage of electronic ballasts is that you can fire either a HPS or MH). But the biggest plus is a 600W HPS will provide 240% more lumens with 18% less power consumption with better penetration.

As far as ballasts, get one with a warranty from a reputable retailer. Prices can vary widely. Run it by the ppl here to make sure you are getting a good deal. Get an air cooled hood. Amazon has some decent prices on light set-ups.

Yes, this thread did drift into something different, but it is still about getting you the best crop that you can get.