If you want to actually grow citrus indoors, rather than just keeping them alive over winter, you will probably want either high intensity discharge lighting (HID) such as metal halide (MH) or high pressure sodium (HPS) - or strong LED lighting such as chip on board (COB) LEDs.

Your six foot ceilings will limit you, however. That may seem like a lot of space, but it will disappear quickly. Factor in the height of your containers (at least a foot), the space needed between your lights and the tops of your plants (1-2 feet depending on the light), and the height of the light itself as well as whatever you use to hang it (for HID, this may be up to a foot), and that six feet can be reduced to as little as two feet - for the height of the plants themselves. That's not a tall plant!

LED may work better in this case because the fixtures can be much slimmer, which will give you a bit more overhead room. You may also want to look at high output T5 fluorescent lighting. It is less powerful than HID or LED, but the fixtures will also be slimmer, and it can be placed as close as 2-4 inches from the tops of your plants.

All of those lighting options can be Googled for more information. I would also suggest you post on the citrus forum here, because it is a lot more active than this one.