For optimal yields, you want at least 100W of HID light per plant. If you're doing 9 plants, get two 600W or a 1000W. For 4 plants, 400W should be fine. For 6 plants, 600W should do it, but more is always better (as long as you keep heat under control).
I definitely recommend HID as opposed to LED or CFL. Everyone has a different opinion but the best yields typically come from HID (MH or HPS). CFL is a little harder to manage, read up about that in the CFL sub-forum under indoor growing. I recommend starting out with 6 plants under a 600W light, and see how you do with that before you invest any further. If you're just starting out, hydroponics isn't really necessary. Grow in some Fox Farm Ocean Forest and read up on agroponics. It's the best way to learn how your plant works, and less to worry about. People think that the only way to get good yields is with hydroponics but that's absolutely not true. The best thing you can give your plant is tlc (tender love and care), as I profess to everyone. Spend your first grow messing up and learning how your plant works and grows and thrives and then move on to bigger and [allegedly] better things.
I recommend checking out HTG Supply for an entry-level 600W system. Make sure you're buying one with an air-coolable hood (the cheapo systems on the website that come with everything generally include shitty cheap reflector hoods, but there are options to swap it for a better one). I recommend the EasyCool 6. It's cheap and effective. Also buy some 6" tubing and their 6" inline fan (250CFM). You WILL need air cooling inside a grow tent. If you have the money, also invest in a centrifugal fan (aka squirrel cage fan, because it looks like a hamster wheel) for moving air out of your grow room so it is replenished with CO2. Don't worry about all the fancy stuff like CO2 units and carbon filters until you really understand how this all works.
If you decide you like growing, add in some more plants and another 600W HID system. You definitely want to use MH bulbs for veg and HPS for flowering. That's the most consistent and reliable way to grow.
Any further questions I'd be happy to answer, but I'm not as experienced as some. I'm just sharing the knowledge I've picked up on this forum over the past month. I'm a novice myself but everything I've told you here is backed up by info on this forum.
Good luck