A good setup- Tek Elite at the minimum or ATIs- of T5s will easily compare, and in some cases beat halides. They have a much different look than halides, they are flourescents, so they will lack substantial shimmer. Some people preferthem, others don't.
I would look at the 8x54 or 8x80 Sunpowers or PowerModules by ATI. Either would work well. The SunPower is cheaper, but just as effective as the PowerModule....the PM is more fnacy and showroom-ish.
The cheapest way would be replace your current ballast. i would do that if you have been happy with your light setup and its results.