Wrote it myself actually. I worked as an engineer for a company that made lighting ballasts for a while, so I'm pretty familiar with how all that stuff works. I'm glad the information was helpful.

I would like add a few things though, for instance, you can get some really good deals on bulbs and grow lights from High Tech Garden Supply. A full 400W HPS grow light system is only about $130 and that's with a bulb and with shipping included. Also, a high-output 400W HPS horticulture bulb is only $30. Admittedly, the bulb is generic, but when I had a problem with mine and they replaced it for free, so the service is great. I mentioned their eBay store already, but the deals are a bit better on their web site.

Also, this may change, but Wal-Mart, Home Depot, and Lowe's all have cheap 4-foot fluorescent fixtures for $8-$9. The main difference is, Lowe's cheap fluoro fixtures are strip lights (ie, no reflectors) and Home Depot and Wal-Mart both have lights with reflectors. I actually like the ones with no reflectors better, because you can pack them more closely together for more light.