They like high intensity light, I'd go with MH's, 400w 14k, if you want whiter light, then 12k. My frogspawn sits about 12 inches under a 400w 14k and it is growing like a weed!!! I'm sure I'm a little overkill, but someone will pipe in and school us both on this subject shortly.
What is the current bulb you have? I understand that it is 65 watt, but is it VHO, PC, or T-5? IMO, I would stick with the same type of bulb. You are also going to have to think about the water heating. You may want to purchase a fan.
I currently have VHO, but the problem is I have a total of four lights on my tank right now. Two 18" 15W 50/50, and two corallife fixtures that hold two 9W compact Fluorecents. One 10K and one actinic. So I would have to upgrade all my lights.
I would go with something the length of your tank. The T-5s are space savers and so are the PCs. I would choose between those that way you can fit as many as you want over top. Well at least with the 18 inches you have. What is the length of the tank?