I use the Hagen GLO, they are pretty bright (blindingly so). I got them and two T5 HO
24watt 24" bulbs totaling to only about 130dollars at my LFS
. The nice thing about the Hagen is that they don't use specialized bulbs like the coralife any T5HO 3/8" tube will work.
They also make Hagen 36" for fixtures your size, the bulbs however, are harder to find.