Well, let's start with some math... 6 x 40w - 240w vs. 400w. Yes, it is likely that you will benefit from the upgrade. Not to mention that the HID light will put out a range of spectrum over a much wider area and with greater penetration which can not be achieved with a fluorescent bulb. Concerning which light is suitable for your situation, you can get a kit that includes the ballast, the cable and socket, the hood, and even the bulb. Or you can purchase components separately. It depends on your needs. I say go for a kit. It will get you where you need to be. Just consider the venting issues as you will have more heat with and HID.