I went with the Twilight units that had the built-in timmer/dimmer with moonlights. I know that evergrow is going to release a similar fixture towards the end of the month. Just make sure that you confirm the LED placement before your order. Otherwise it will be a crap shoot to what your light is going to look like. I would think that one of these type fixtures should be enough to cover your tank.
Have you gotten yours in and on your tank yet?